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MOTION SAMPLE BOOKLET CLASS X
• ELECTRICITY
• CHEMICAL REACTIONS AND EQUATIONS
• NUTRITION
• REAL NUMBER
• WORK LIFE & LEISURE
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CLASS - X
THEORY AND EXERCISE BOOKLET
CONTENTS
ELECTRICITY
S.NO.
TOPIC
PAGE NO.
THEORY ..............................................................................................
5 – 21
SOLVED EXAMPLE .............................................................................
22 – 29
EXERCISE - I .......................................................................................
30 – 33
EXERCISE -II .......................................................................................
34 – 38
CHEMICAL REACTIONS AND EQUATIONS
S.NO.
TOPIC
PAGE NO.
THEORY ..............................................................................................
39 – 60
SOLVED EXAMPLE .............................................................................
61 – 70
EXERCISE - I .......................................................................................
71 – 73
EXERCISE -II .......................................................................................
74 – 77
NUTRITION
S.NO.
TOPIC
PAGE NO.
THEORY ..............................................................................................
78 – 86
SOLVED EXAMPLE .............................................................................
87 – 87
EXERCISE - I .......................................................................................
88 – 89
EXERCISE -II .......................................................................................
90 – 90
THEORY AND EXERCISE BOOKLET
CONTENTS
REAL NUMBERS
S.NO.
TOPIC
PAGE NO.
THEORY ..............................................................................................
91 – 92
SOLVED EXAMPLE .............................................................................
93 – 97
EXERCISE - I .......................................................................................
98 – 102
EXERCISE -II .......................................................................................
103 – 103
EXERCISE -III ......................................................................................
104 – 109
WORK, LIFE AND LEISURE
S.NO.
TOPIC
PAGE NO.
THEORY ..............................................................................................
110 – 117
EXERCISE - I .......................................................................................
118 – 119
EXERCISE -II .......................................................................................
120 – 120
Page # 5
ELECTRICITY
ELECTRICITY
ELECTRIC CHARGE
(A)
(B)
Definition: Electric charge may be defined as the intrinsic property of certain fundamental particles
(electron, proton, etc) due to which they produce electric and magnetic effects.
Charge on a Macrobody: Excess or deficiency of electrons in a body is equal to the charge on a
macrobody. A body having excess of electrons in negatively charge and a body having deficiency of
electrons is positively charged.
From the study of atomic structure, we know that an atom consists of a central part called nucleus
and around the nucleus there are a number of electrons revolving in different paths or orbits. The
nucleus contains protons and neutrons. A proton is a positively charged particle while a neutron has no
charge. Therefore, the nucleus of an atom bears a positive charge. An electron is a negatively charged
particle having negative charge equal to the positive charge on a proton. Normally, the number of
electrons is equal to the number of protons in an atom. Therefore, an atom is neutral as a whole; the
negative charge on electrons cancelling the positive charge on protons. This leads to the conclusion
that under ordinary conditions, a body is neutral i.e. it exhibits no charge.
When this equity or balance is disturbed by removing or supplying electrons, the body acquires a net
charge. The body will acquire a positive or negative charge depending upon whether electrons are
removed from it or added to it.
(C)
Types of Electric Charge: There are two types of charges. They are:
(i) Positive charge: A body having deficiency of electrons.
(ii) Negative charge: A body having excess of electrons.
(D)
Charging of a Body: There are a number of methods to charge a body as:
(i) Charging by friction
(ii) Charging by conduction
(iii) Charging by induction etc.
We will discuss charging by friction in detail:
Whenever two bodies (at least one non conductor) are rubbed against each other, heat is produced
due to friction present between them. Due to this heat produced, electrons in both the bodies are
excited. The body having more electron affinity attracts some of the electrons from other body. Both
the bodies develop equal and opposite charges by this method.
S.No.
(E)
Positive charge
Negative Charge
1
Glass Rod
2
Fur or woolen clot h Ebonit e, Amber, Rubber rod
3
Woolen coat
Plast ic seat
4
Woolen carpet
Rubber shoes
5
Nylon or Acet at e
Clot h
6
Dry hair
Comb
Silk clot h
Properties of Electric Charge:
(i) Like charges repel and unlike charges attract each other.
(ii) Charge is a scalar quantity.
(iii) Charge is always quantized.
(iv) Charge is conserved.
(v) Charge is always associated with mass.
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(F)
ELECTRICITY
Unit of Charge: The charge on an electron is so small that it is not convenient to select it the unit of
charge. In practice, coulomb is used as the unit of charge, i.e. SI unit of charge is coulomb abbreviated
as C. One coulomb of charge is equal to the charge on 625 × 10 16 electrons.
1 coulomb = charge on 625 × 1016 electrons or 6.25 × 1018 electrons
Thus, when we say that a body has a positive charge of one coulomb (i.e + 1C) it means that the body
has a deficit of 625 × 10 16 electrons from the normal due share.
Newton's Thought
If a neutral body is made positively charged, is there any change in its mass?
Explanation
In charging any neutral body, the mass of a body changes, though the change
is extremely small or negligible. If a neutral body is made positive, it means
electrons are removed from it. Thus, the mass of body decreases.
STATIC AND CURRENT ELECTRICITY
(A)
(B)
Static Electricity: A branch of physics which deals with the study of the electric charges at rest and
their effects is known as electrostatic or static electricity.
Current Electricity: A branch of physics which deals with the study of the electric charges in motion
and their effects is known as current electricity.
ELECTRIC FIELD AND ELECTRIC POTENTIAL
(A)
Electric Field: Electric field due to a given charge is defined as the space around the charge in which
electrostatic force of attraction or repulsion due to charge can be experienced by any other charge. If
a test charge experiences no force at a point, the electric field at that point must be zero.
Electric field intensity at any point is the strength of electric field at that point. It is defined as the
force experienced by unit positive charge placed at that point.
If F is the force acting on a test charge +q0 at any point r, then electric field intensity at this point is
given by
E
F
q0
Electric field is a vector quantity and its S.I. unit is Newton per coulomb or N/C.
(B)
Electric Potential: The electric potential at a point in an electric field is defined as the amount of work
done in moving a unit +ve charge from infinity to that point, without acceleration or without a change
in K.E. against the electric force Mathematically.
V
W
q
Since work is measured in joule and charge in coulomb, therefore electric potential is measured in joule
per coulomb (J/C). This unit occurs so often in our study of electricity, so it has been named as volt, in
honour of the scientist Alessandra Volta (the inventor of the voltaic cell).
1 V olt
1 jo ule
1 cou lom b
Potential is a scalar quantity, therefore it is added algebraically. For a positively charged body potential
is positive and for a negatively charged body potential is negative.
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Page # 7
ELECTRICITY
(C)
Electric Potential Difference: Consider a charge Q placed at a point P. Let A and B be two other
points (B being closer to A) as shown in figure.
Q
B
q
A
P
From infinity
If a charge q is brought from infinity to A, work WA will be done.
The potential at A will then be, VA
WA
q
If charge q is brought from infinity to B, the work done will be WB.
The potential at B will then be, VB
WB
q
The quantity V B – VA is called the potential difference between points A and B in the electric field of
charge Q. Mathematically we have,
VB
VA
WB
WA
q
q
Electric potential difference is also measured in volt.
ELECTRICITY
The source of all electricity is charge. As charge is the basis of all electrical phenomena, we need to
know the amount of charge on a body. It is measured in coulombs. The coulomb is the SI unit of charge
and its symbol is C.
Matter is generally made of protons, electrons and neutrons. Each proton carries a charge of
1.6 × 10 –19 coulomb, and each electron carries an equal negative charge. Neutrons do not carry any
net charge. Normally, a body has equal number of protons and electrons, and is therefore, electrically
neutral. In certain situations, the balance of charges in a body is disturbed.
For example:- when a glass rod is rubbed with a silk cloth, some electrons get transferred from the
glass rod to the silk. The silk cloth, which gains electrons, becomes negatively charged. And the glass
rod, which is left with more protons than electrons, becomes positively charged.
Charged particles or objects can exert forces on each other. While like (similar) charges repel each other,
unlike charges attract. Another important thing about charged particles is that they can flow, i.e., they
can move in a particular direction. This flow of charged particles is called an electric current. Charged
particles such as electrons are present in all substances. But they do not flow on their own. For flow of
charges, there has to be a potential difference.
POTENTIAL DIFFERENCE AND THE FLOW OF CHARGE
Charges
q
A
B
The potential difference between two points A and B is the work done per unit charge in taking a
charge from B to A. We express this mathematically as
V
VA – VB
W
q
Here, V is the potential difference between the points A and B, and V A and VB are the potentials at
these points. The potential at infinity is chosen as zero.
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ELECTRICITY
If B be the reference point, the potential at B is V B = O. From Equation, the potential at A is
V A = W/q. So, the potential at a point is the work done per unit charge in taking a charge to that point
from a chosen reference point. Equation may also be written as
W= qV.
The work done on the charge q is stored as the electric potential energy (U) of the group of charges.
So,
U = qV
UNIT OF POTENTIAL DIFFERENCE
The unit of potential difference (and potential) is the volt, whose symbol is V. One volt is the potential
difference between two points in a current carrying conductor when 1 joule of work is done to move a
charge of 1 coulomb from one point to the other.
1 J oule
1 Co ulomb
1 volt or 1 V
1 J C –1
The potential difference between two points is sometimes also called the voltage.
FLOW OF CHARGE
Consider two identical metallic spheres P and N, carrying equal amounts of positive and negative charges
respectively. A positive charge is to be taken from B to A. It is attracted by the negatively charged
sphere N and repelled by the positively charged sphere P. So, to move the charge towards A, one has to
apply a force on it towards the left. Thus, the work done is positive. Hence, the potential difference VA
– V B is positive. This means V A > V B'
As one moves towards P, the work done increases; so, the potential increases. And on moving towards
N, the potential decreases. So, the potential of P is higher than that of N. In general, the potential of
a positively charged body is taken as higher than that of a negatively charged body.
+
–
+
+
+
+
A
+
P
Repulsion
B
+
+
+
–
–
Attraction –
N
–
–
–
–
What happens when a free-to-move charge is placed between the spheres? A positive charge will
move towards the negatively charged sphere. And a negative charge will move towards the positively
charged sphere. That is, a free positive charge moves towards lower potential. And a free negative
charge moves towards higher potential.
If the two spheres are connected by a metal wire, electrons from the negatively charged sphere (at a
lower potential) will flow to the positively charged sphere (at a higher potential). Eventually, the flow
of electrons causes the charges on the spheres to become balanced. When that happens, the spheres
no longer carry a net charge, and therefore, have equal potential. So, the flow of electrons stops. So
we can say that a potential difference causes charges to flow.
+
+
+
+
Electrons
+
+
+
Higher
potential
(a)
–
– –
–
–
–
–
Lower
potential
(b)
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Page # 9
ELECTRICITY
A CELL PROVIDES A CONSTANT POTENTIAL DIFFERENCE
The potential difference provided by things like charged spheres reduces to zero quickly once charges
start to flow. So, we have to use cells to provide constant potential difference for a long time. Cells
have chemicals inside. Reactions in the cell cause positive and negative charges to gather separately.
This creates a potential difference between the terminals of the cell. The terminal at a higher potential
is called the positive terminal and the one at a lower potential is called the negative terminal.
The cells that we commonly use are called dry cells (Figure). In a common dry cell, the small metallic
cap at one end is the positive terminal, while the flat metallic plate at the other end is the negative
terminal. It provides a potential difference of 1.5 V. A cell is represented by the symbol shown in fig
(b). The larger line represents the positive terminal, while the shorter line represents the negative
terminal.
A COMBINATION OF CELLS IS CALLED A BATTERY
Quite often, multiple cells are combined to get a potential difference that is higher than that of a single
cell. For example, we connect two 1.5V cells to get a potential difference of 3V (Figure (c)) This is
shown using symbols in Figure (d).
+
–
1.5V
Negative
terminal
Positive
terminal
(a)
1.5V
–
+
A battery of two cells to provide 3 volts
(b)
(c)
(d)
ELECTRIC CURRENT
Consider a metallic wire ACB connected across a cell of potential difference V. Since the end A is
connected to the positive terminal, it is at a higher potential than the end B. In metals, some electrons
are loosely bound to the atoms, and can move within it. These are called free electrons. In the metallic
wire, these electrons (negative charges) move from the low-potential side B to the high-potential side
A. After reaching A, they enter the cell. The chemical reactions in the cell drive these electrons to the
negative terminal. From there, they re-enter the wire at the end B. Thus, there is a continuous flow of
electrons in the wire from B to C to A. We say that there is an electric current in the wire. In a metal,
the flow of negative charges constitutes the current.
Direction of current
C
A
B
Current in a wire connected to a cell
An electric current can also be a flow of positive charges. So, a flow of charge is called an electric
current.By convention, the direction of current is taken as the direction of flow of positive charges.
Thus, the direction of current is opposite to the direction of flow of negative charges. So, when a
wire is connected to a cell, the current in the wire is from the positive-terminal end to the
negative-terminal end.
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ELECTRICITY
MEASUREMENT OF CURRENT
The charge passing per unit time through a given place(area) is the magnitude of the electric current
at that place. Thus,
i
Q
t
Here Q is the charge that passes through a place in time t.
Unit of current From Equation, we find that current is charge divided by time. The SI unit of charge is
the coulomb and that of time is the second. The SI unit of current, therefore, is coulomb / second.
This unit is called the ampere, whose symbol is A.
Thus, if one coulomb of charge passes through a place in one second, the current there is 1 ampere.
CONDUCTORS AND INSULATORS
Materials that conduct electricity easily are called good conductors or simply, conductors. And, materials
that do not conduct electricity easily are called insulators.
All metals conduct electricity because they have some loosely bound free electrons, which flow when
a potential difference is applied. However, some metals conduct electricity better than others. Silver is
the best conductor. But because of the high cost of silver, electric wires are made of copper, or in some
cases aluminium.
Most nonmetallic solids do not conduct electricity. Although diamond and graphite are both forms of carbon
(a nonmetal), graphite is a conductor while diamond is an insulator. Insulators do not conduct electricity
because their electrons are tightly bound to the atoms. Rubber, plastics, wood, glass and porcelain are
some examples of insulators. Insulators have many uses. For example, they are used as protective covers
on electric wires and electrician's tools.
Certain liquids also conduct electricity. While distilled water is an insulator, addition of certain salts,
acids or bases allows it to conduct electricity. Under normal circumstances, gases do not conduct
electricity.
ELECTRIC CIRCUITS AND MEASURING INSTRUMENTS
A closed path in which a current can flow is called an electric circuit. An electric circuit may have
one or more electric elements such as bulbs (or lamps), cells, switches (or plug keys), metal wires, etc.
Each element of a circuit has a specific function to play. For example, wires can be used to connect
one element to the next. And a plug key or a switch can be used to either complete or break the closed
path, thereby starting or stopping the current in the circuit.
Some common circuit elements and their symbols are shown in Figure.
+
Bulb (lamp)
Plug key (OFF)
Switch (OFF)
Resistor
Unconnected
conductor
Ammeter
+
Fuse
Plug key (ON)
Switch (ON)
Variable Resistor
(rheostat)
Connected
conductors
Voltmeter
Fig. Some symbols used in circuit diagrams
COMMON MEASURING INSTRUMENTS
The electric current in a circuit is measured by an instrument called the ammeter, and the
potential difference between two points in it is measured by a voltmeter (in voltage stabilizers).
In these meters, a needle moving over a graduated scale gives the value of the measured quantity.
Each meter has two terminals. The terminal marked '+' is connected by a wire to the higher-potential
side of a circuit, while the terminal marked '–' is connected to the lower-potential side.
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ELECTRICITY
USING AN AMMETER TO MEASURE CURRENT
To measure the current through an element of a circuit, an ammeter is connected in such a way that
the current flowing through it also flows through the element. Such a connection is called a series
connection. In Figure, the current i flowing through the lamp also flows through the ammeter. The
reading of the ammeter gives the current through the lamp. Note that if the ammeter is removed, there
will be a gap, and the current through the circuit will stop.
i
+
A
–
Ammeter in a circuit
Two or more electric elements are said to be connected in series if the current flowing through
one also flows through the rest.
An ammeter is always connected in series in a circuit.
USING A VOLTMETER TO MEASURE POTENTIAL DIFFERENCE
Figure shows a circuit that has two lamps connected to a cell. We want to measure the potential
difference across the lamp L2 , i.e., between the points A and B. As A is on the side of the positive
terminal of the cell, its potential is higher than that of B. So, the '+' terminal of the voltmeter is
connected to A, and the '–' terminal, to B. The reading of the voltmeter gives the potential difference
across L2. The current flowing through the voltmeter is different from those flowing through the other
elements of the circuit. Also, even if the voltmeter is removed, the current continues to flow in the
circuit. Note that the potential difference across L 2 and the voltmeter is the same. Such a connection
is called a parallel connection.
i2 +
i
L1
V
–
i1
A
L2
B
Voltmeter in a circuit
Two or more electric elements are said to be connected in parallel if the same potential difference
exists across them.
OHM'S LAW
The electric current through a metallic element or wire is directly proportional to the potential difference
applied between its ends, provided the temperature remains constant.
If a potential difference V is applied to an element and a current i passes through it,
i
V
or i =
Thus Ohm's Law
1
V
R
V = iR
i (A)
1ohm
1 volt
1 amp ere
V (volt)
Here R is a constant for the given element (metallic wire) at a given temperature and is called its
resistance. It is the property of a conductor to resist the flow of charges through it.
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ELECTRICITY
RESISTANCE
From equation,
i
V
R
So, for a given potential difference,
i
1
R
Thus, for a given potential difference, the current is inversely proportional to the resistance. The
higher is the resistance, the lower is the current. If the resistance is doubled, the current is halved.
Good conductors have low resistance, while insulators have very high resistance.
UNIT OF RESISTANCE
Potential difference is measured in volts, and current is measured in amperes. From Equation, R = V/
i. So, the unit of resistance is volt/ampere. This unit is called the ohm, and its symbol is . We can
define one ohm as follows.
If a potential difference of 1 volt is applied across an element, and a current of 1 ampere passes
through it, the resistance of the element is called 1 ohm.
ON WHAT DOES RESISTANCE DEPEND ?
The resistance of the conductor depends on:
(i) on its length
(ii) on its area of cross-section
(iii) on the nature of its material
(iv) Resistance depends on temperature (resistance increases with increase in temperature)
Resistance of a uniform metallic conductor is directly proportional to its length ( ) and inversely
proportional to the area of cross-section (A).
R
1
A
R
Combining eqs. we get
Where
and R
or R
A
A
(rho) is a constant of proportionality and is called electrical resistivity of the material of the
conductor.
RESISTIVITY ( ) : Here,
is a constant for a given material at a given temperature. It is called the
resistivity of the material. the resistivity of a material is the resistance per unit length of a unit cross
section of the material. The SI unit of a material depends on its temperature. For metals and alloys of
metals, the resistivity increases with rise in temperature. The SI unit of resistivity is
m.
Material
Metals
Alloys
Semiconductors
Insulators
Silver
Copper
Aluminium
Tungsten
Iron
Manganin
Nichrome
Germanium
Silicon
Diamond
Fused quartz
Resistivity
1.6 × 10 –8
1.7 × 10 –8
2.8 × 10 –8
5.8 × 10 –8
9.7 × 10 –8
48.2 × 10–8
100 × 10–8
4.7 × 10 –3
2.5 × 103
5 × 1012
1016 – 10 19
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ELECTRICITY
Newton's Thought
Two materials have different resistivities. Two wires of the same length are
made, one from each of the materials. Is it possible for each wire to have the
same resistance?
Explanation
Two wires of the same length are made, one from of the materials. The resistance
of a wire is given by, R
A
cross-sectional areas of the wires are chosen so that the ratio
A
is the same for
each. That is
A
2
or 2
2
A1
A2
A1
1
This is the condition for each wire of different materials to have the same
resistance when they have same length.
R3 B
R2
A R1
1
V1
V2
V3
V
A series combination of resistors
SERIES AND PARALLEL CONNECTIONS OF RESISTORS
A conducting material (e.g., a wire) of a particular resistance meant for use in a circuit is called a
resistor. A resistor is sometimes simply referred to as a resistance. It is represented by the symbol
. Two or more resistors can be connected in series, in parallel or in a manner that is a combination
of these two.
1.
SERIES CONNECTION OF RESISTORS
Two or more resistors are said to be connected in series if the current flowing through one also flows
through the rest.
The total potential difference across the combination of resistors connected in series is equal to the
sum of the potential differences across the individual resistors.
V
V1
V2
V3
EQUIVALENT RESISTANCE IN SERIES CONNECTION
Figure (a) shows three resistors of resistances R 1 , R2 and R3 connected in series. The cell connected
across the combination maintains a potential difference V across the combination. The current through
the cell is i. The same current i flows through each resistor.
Let us replace the combination of resistors by a single resistor R eq such that the current does not
change, i.e., it remains i. This resistance is called the equivalent resistance of the combination,
and its value is given by Ohm's law as Req = V/i
Thus
V = iR eq.
(a)
(b)
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ELECTRICITY
The potential differences V1 , V2 and V3 across the resistors R1 , R2 and R3 respectively are given by
Ohm's law as :
V 1 = iR1 , V2 = iR2 , V3 = iR3
Since the resistors are in series,
V = V 1 + V2 + V3
Substituting the values of the potential differences in the above equation,
iReq = iR1 + iR2 + iR3
or
iReq =i(R1 +R2 +R3)
or
R eq = R 1 + R 2 + R3
Similarly, for n resistors connected in series,
Equivalent resistance of resistors in series : R e q = R 1 + R 2 + R 3 + .... . + R n
2.
PARALLEL CONNECTION OF RESISTORS
The total current flowing into the combination is equal to the sum of the currents passing through the
individual resistors.
i
i1
i2
i3
If resistors are connected in such a way that the same potential difference gets applied to each of
them, they are said to be connected in parallel.
EQUIVALENT RESISTANCE IN PARALLEL CONNECTION
Figure (a) shows three resistors of resistances R1, R2 and R3 connected in parallel across the points A
and B. The cell connected across these two points maintains a potential difference V across each
resistor. The current through the cell is i. It gets divided at A into three parts i 1 , i2 and i3 , which flow
through R1 , R2 and R3 respectively.
R1
i1
i2
A
R2
Req
B
R3
i3
i
i
i
V
(a)
V
(b)
Let us replace the combination of resistors by an equivalent resistor R eq such that the current i in the
circuit does not change (Fig). The equivalent resistance is given by Ohm's law as Req = V/i.
Thus,
i=
V
Re q
The currents i1 , i2 and i3 through the resistors R1, R2 and R3 respectively are given by Ohm's law as
i1 =
V
,
R1
i2 =
V
V
, i3 =
R2
R3
Since the resistors are in parallel,
i = i1 + i2 + i3
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ELECTRICITY
Substituting the values of the currents in the above equation,
V
V V V
=
+
+
R e q R1 R2 R 3
or
1
1
1
1
=
+
+
R e q R1 R2 R 3
Similarly, if there are n resistors connected in parallel, their equivalent resistance Req is given by
Equivalent Resistance of resistors in parallel :
1
1
1
1
=
+
+.......+
Req R1 R2
Rn
For two resistances R1 and R2 connected in parallel,
1
1
1
R + R2
=
+
= 1
R R1 R2
R1 R 2
or
R
R1R2
R1 + R2
The equivalent resistance in a parallel connection is less than each of the resistances.
When a resistance is joined parallel to a comparatively smaller resistance, the equivalent resistance is
very close to the value of the smaller resistance.
NOTE : If a resistor connected in series with others is removed or fails, the current through each
resistor becomes zero. On the other hand, if a resistor connected in parallel with others fails or is
removed, the current continues to flow through the other resistors.
DISTRIBUTION OF CURRENT IN TWO RESISTORS IN PARALLEL
Consider the circuit in fig. The resistors R 1 and R2 are connected in parallel. The current i gets
distributed in the two resistors.
i = i1 + i2
.....(i)
Applying Ohm's law to the resistor R1
V A – VB =R1 i1 ·
.....(ii)
And applying Ohm's law to the resistor R2
V A – VB = R2i2
From (ii) and (iii),
R1i1 = R2 i2 or i2
.... (iii)
R1
i
R2 1
Substituting for i2 in (i), we have
R1
R
R + R2
i = i 1 + 1 = i1 1
i = i1 +
R2 1 1
R2
R2
R
2
or i1 = R + R i
1
2
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i1
R1
i2
R2
A
B
i
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Page # 16
ELECTRICITY
Similarly,
i2 =
R1
i
R1 + R 2
i1 R2
=
i2 R1
Thus,
The current through each branch in a parallel combination of resistors is inversely proportional to its
resistance.
Newton's Thought
Figure shows a combination of four identical bulbs joined with a battery.
Compare the brightness of the bulbs shown. What happens if bulb A fails, so
that it cannot conduct current? What happens if bulb C fails? What happens
if bulb D fails?
Explanation
Bulbs A and B are connected in series across the emf of th battery, whereas
bulb C is connected by itself across the battery. This means the voltage
drop across C has the same magnitude as the battery voltage, whereas this
same voltage is split between bulbs A and B. As a result, bulb C will glow
more brightly than either of bulbs A and B, which will glow equally brightly.
bulb D has a wire connected across it i.e., a short circuit, so that potential
difference across bulb D is zero and it doesn't glow. If bulb A fails, B goes
out, but bulb C will glow. If bulb C fails, there is no effect on the other bulbs.
If bulb D fails we cannot detect this event, because bulb D was not glowing
initially; also, there is no effect on the other bulbs.
A
B
C
D
DEVICES IN SERIES AND PARALLEL
You must have seen tiny bulbs strung together for decorating buildings during festivals like Diwali, and
occasions like marriages, etc. These bulbs are connected in series, and the mains voltage is applied to
the combination. The potential difference (V) of the mains gets divided across the bulbs (V = V1 + V 2 +
V 3 + ... ). So, a small potential difference exists across each bulb, close to that required to make the
bulb work. However, the same current flows through all the bulbs. So, if one bulb goes bad, the current
through it stops, and this stops the current through the rest of the bulbs as well. To make the chain of
lights work, we have to find and replace the defective bulb. This problem does not occur with the lights
in our house. That is because in houses, lights, fans, etc., are connected in parallel. In parallel
connection, the same mains voltage gets applied to each device, but the current through each is
different. If one of them goes bad, the current in the other branches of the parallel connection does
not stop. Another advantage of parallel connection is that, unlike series connection, each device can
draw a different current, as per its requirement.
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ELECTRICITY
HEATING EFFECT OF ELECTRIC CURRENT
When an electric current passes through a bulb, the filament gets so hot that it glows and emits light.
When a current passes through the filament of an electric iron, the iron becomes very hot. This
increase in temperature is due to what is called 'the heat produced due to current'.Suppose a resistor
R is connected to a cell. The cell maintains a potential difference V across the resistor, driving a
current i through it.
So,
V = iR
......(i)
R
i
V
The current through the resistor is actually a flow of negative charges (electrons). Inside the cell, the
negative charges flow from the positive to the negative terminal. The cell does work = QV to take a
charge through the potential difference V between its terminals. This increases the energy of the
charge by QV. This increased energy gets converted to heat in the resistor. So, the energy appearing
as heat is given by
U = QV
......(ii)
The charge that passes through the wire in time t is
Q =it.
......(iii)
Using (i), (ii) and (iii), we find that the heat produced in the wire in time t is
U =QV = (it) (iR) =i2 Rt.
From Equation the heat produced is proportional to the square of the current, if R and t remain
constant. So, if the current passing for a given time through a given resistance is doubled, the heat
produced becomes four times. Similarly, for a given i and t, the heat produced is proportional to R. If
the same current i passes through two resistances in a given time, more heat will be produced in the
larger resistance. The heat produced can also be written as.
U = i2 Rt =
or
U=
V
R
2
Rt
V2
t
R
For a given V and t, the heat produced is inversely proportional to R. So, if the same potential
difference is applied across two resistances, more heat will be produced in the smaller resistance.
We have seen above that the increased energy of a charge gets converted to heat in the resistor. The
increase in energy comes from the work done by the cell. This uses up the chemical energy of the cell.
So, the energy appearing as heat in the resistor ultimately comes at the expense of the chemical
energy of the cell.
Not always is the work done by a cell converted to heat. Immediately after a motor is connected to a
cell, the speed of the shaft of the motor increases. A part of the work done by the cell goes into
producing the increase in kinetic energy. And a part is used to overcome friction, etc. When the motor
achieves a constant speed, its kinetic energy does not change. So the work done by the cell is only
used to overcome friction, etc. This appears as heat. That is why the cover over a motor becomes
warm on use.
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ELECTRICITY
APPLICATIONS OF THE HEATING EFFECT OF CURRENT
The heating effect of electric current has many uses. Electric bulbs, room heaters, electric irons,
immersion heaters, toasters, electric fuses and a number of other appliances work on this principle. In
all of these, a wire of suitable resistance, commonly called the heating element, is connected to the
power supply. The current passing through the element produces heat in it, which is used for some
specific purpose.
(i)
Electric bulb: An electric bulb has a simple structure. It consists of a sealed glass bulb that has a
tungsten filament connected to two electrical contacts. The bulb is filled with an unreactive gas like
argon or nitrogen. To produce white light, the filament has to be heated to about 3000°C by passing a
current through it. Obviously, the material of the filament should such that it does not melt at this
temperature. Tungsten is used for the filament because its melting point is about 3400°C. The sealed
glass bulb serves two purposes. First, it protects the filament from oxidation and the effects of
humidity. Secondly, the small enclosed volume makes it easier to maintain the required temperature, as
without it the loss of heat would be more.
(ii)
Fuse: A fuse is a safety device that does not allow excessive current to flow through an electric
circuit. It consists of a metallic wire of low melting point, fixed between the two terminals of a fuse
plug. The fuse plug fits into a fuse socket connected in the circuit. Fuses are available in various
shapes. The fuse plug is used in household wiring. It is made of porcelain.
A fuse is connected in series with an appliance (such as a TV) or a group of appliances (such as the
lights and fans in a room). So, the current through the fuse is the same as the current through the
appliance or the group of appliances. If this current exceeds a safe value, the heat produced in the fuse
wire causes it to melt immediately. This breaks the circuit, preventing any damage. Figure shows
examples of how a fuse is connected in circuits.
Good-quality fuse wires are made of tin, as it has a low melting point. Some fuse wires are made of an
alloy of tin and copper. The thickness of the fuse wire depends on the circuit in which it is to be used.
If a section of the circuit is meant to carry a maximum of 5A current, the fuse wire should also be able
to carry currents up to 5A. Similarly, for wiring meant for 15A, the fuse wire should be thicker, and
should be able to carry currents up to 15A.
12V
12V
(a)
(b)
DISADVANTAGES OF THE HEATING EFFECT OF CURRENT
A current always produces some heat, whether we use the heat or not. If the heat produced cannot
be utilized, it represents a wastage of energy. A considerable amount of energy is thus wasted in the
transmission of electricity from the generating station to our homes. Sometimes, the heat produced in
a device is so much that it can damage the device, unless proper cooling arrangements are made. To
dissipate the heat produced in TV sets, monitors, etc., their cabinets have grills for air to pass. Certain
components of a computer get so hot that they have fans to cool them.
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Page # 19
ELECTRICITY
ELECTRIC POWER
Power is the rate of doing work, or the rate at which energy is produced or consumed. The electrical
energy produced or consumed per unit time is called electric power. In an electric circuit, the power is
P=
Using
U
t
i2 Rt
t
i2 R
iR = V
P = Vi
P=
V2
R
The energy consumed and power are related as
U = Pt.
UNIT OF POWER
The SI unit of energy is the joule, and that of time is the second. The SI unit of power is therefore
joule/second. This unit is called the watt, whose symbol is W.
RATING OF ELECTRIC APPLIANCES
Take an electric bulb and see what is written on it. Apart from the name and the symbol of the
company, we will find values of power and potential difference. For example, it could be 60W, 220V. It
means that 220V should be applied across this bulb, and when 220V is applied, the power consumed
will be 60W. We will find similar markings on all electric· appliances. For an electric appliance, the values
of power and voltage taken together form what is called the rating of the appliance.
From the rating of an appliance, you can easily calculate its resistance by using the equation P =
V2
.
R
Note that higher the power rating, smaller the resistance. So, a 1000W heater has less resistance than
P
a 100W bulb. We can also calculate the current drawn by an appliance by using the relation i =
.
V
KILOWATT HOUR
Power is the rate of energy consumed or produced. If 1 joule of energy is used per second, the energy
is used at the rate of 1 watt. In other words, if energy is used at the rate of 1 watt, the total energy
used in 1 second is 1 joule. How much energy is used in 1 hour if it is used at the rate of 1000 watt?
It is (1000 watt) × (3600 second) = 3,600,000 joule.
This amount of energy is called 1 kilowatt hour, written in short as kWh.
Thus, 1 kWh =3,600,000 J = 3.6 × 106 J.
The electrical energy used in houses, factories, etc., is measured in kilowatt hours. The cost of
electricity is fixed per kilowatt hour. One kilowatt hour of electrical energy is called one unit.
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ELECTRICITY
ELECTRICAL SAFETY
(A)
Earthing: Earthing means to connect the metal case of electrical appliance to the earth (at zero
potential) by means of a metal wire called "earth wire". In household circuits, we have three wires, the
live wire, the neutral wire and the earth wire. One end of the earth wire is buried in the earth. We
connect the earth wire to the metal case of the electrical appliance by using a three-pinplug.
The metal casing of the appliance will now always remain at the zero potential of the earth. We say
that the appliance has been earthed or grounded. If, by chance, the live wire touches the metal case
of the electric iron (or any other appliance) which has been earthed, then the current passed directly
to the earth through the earth wire. It does not need our body to pass the current and therefore, we
do not get an electric shock. Actually, a very heavy current flows through the earth wire and the fuse
of house-hold wiring blows out or melts. And it cuts off the power supply. In this way, earthing also
saves the electrical appliance from damage due to excessive current.
(B)
Miniature Circuit Breaker: These days a device called a miniature circuit breaker (MCB) is also used
instead of or in addition of fuses, in the household electric circuits. It is a switch that automatically
switches off a circuit if the current in it exceeds the specified maximum limit.
COLOR CODING OF WIRES
An electric appliance is provided with a three-core flexible cable. The insulation on the three wires is of
different colours. The old convention is red for live, black for neutral and green for earth. The new
international convention is brown for live, light blue for neutral and green (or yellow) for earth.
GALVANOMETER
A galvanometer is an instrument that can detect the presence of a current in a circuit. The pointer
remains at zero (the centre of the scale) for zero current flowing through it. It can deflect either to
the left or to the right of the zero mark depending on the direction of current.
Galvanometers are of two types:
(i) Moving coil galvanometer
(A)
(B)
(ii) Moving magnet galvanometer
It is used to make ammeter and voltmeter as follows:
Ammeter: Ammeter is an electrical instrument which measures the strength of current in 'ampere' in a
circuitry which is always connected in series in circuit so that total current (to be measured) may pass
through it. The resistance of an ideal ammeter is zero (practically it should be minimum).
Voltmeter: It is an electrical instrument which measures the potential difference in 'volt' between two
points of electric circuit. The only difference between ammeter and voltmeter is that ammeter has its
negligible (approximately zero) resistance so that it may measure current of circuit passing through it
more accurately giving the deflection accordingly, while the voltmeter passes negligible current through
itself so that potential difference developed due to maximum current passing through circuit may be
measured.
Voltmeter has very high resistance and the resistance of an ideal voltmeter is infinite.
A voltmeter is always connected in parallel.
V
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Page # 21
ELECTRICITY
COLOR CODING OF RESISTORS
Digit
Digit Multiplier
Tolerance
Digit Digit Digit Multiplier
4-band code
Color
5-band code
Digit
Multiplier
Black
0
0
10 (1)
Brown
1
10 1
1
2
10
2
2
Red
Tolerance (%)
Orange
3
10
3
Yellow
4
10
4
Green
5
10 5
0.5
Blue
6
10 6
0.25
7
10
7
8
Violet
Grey
8
10
White
9
10 9
Gold
Silver
Tolerance
10–1
–2
10
(None)
0.1
5
10
20
Note: Short trick for colors:- B B Roy of Great Britain has very good Wife.
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ELECTRICITY
SOLVED PROBLEMS
Ex.1
A piece of wire of resistance R is cut into five equal parts. These parts are then connected in
parallel. If the equivalent resistance of this combination is R', then the ratio R/R' is :
(A) 1/25
(B) 1/5
(C) 5
(D) 25
Sol.
Resistance of each one of the five parts =
R
5
Resistance of five parts connected in parallel is given by
or
1
R'
R
R'
1
R/ 5
1
R/ 5
1
R/ 5
1
R/ 5
1
R/ 5
1
R'
or
5
R
5
R
5
R
5
R
5
R
25
R
25
Ex.2
Thus, (D) is the correct answer.
Which of the following terms does not represent electrical power in a circuit :
(A) I2 R
(B) IR2
(C) VI
(D) V2 /R
Sol.
Electrical power, P = VI = (IR) I = I 2R = V
Ex.3
Obviously, IR2 does not
Thus, (B) is the correct
An electric bulb is rated
will be:
(A) 100 W
(B)
Sol.
V
R
V2
R
represent electrical power in a circuit.
answer.
220 V and 100 W. When it is operated on 110 V, the power consumed
75 W
(C) 50 W
Resistance of the electric bulbs, R =
V
2
(D) 25 W
(P = V 2/R)
P
(2 20 )2
= 484
1 00
or R =
Power consumed by the bulb when it is operated at 110 V is given by
V '2
R
P' =
Ex.4
Sol.
(1 10 )2
4 84
1 10 1 1 0
48 4
25 W
(V' = 100 V)
Thus, (D) is the correct answer.
Two conducting wires of the same material and of equal lengths and equal diameters are first connected
in series and then in parallel in an electric circuit. The ratio of the heat produced in series and
parallel combinations would be :
(A) 1:2
(B) 2:1
(C) 1:4
(D) 4:1
Since both the wires are made of the same material and have equal lengths and equal diameters,
these have the same resistance. Let it be R.
When connected in series, their equivalent resistance is given by
Rs = R + R = 2R
When connected in parallel, their equivalent resistance is given by
1
Rp
1
R
1
R
2
R
or Rp =
R
2
V2
R
V2
Power (or heat produced) in series, P s = R
s
Further, electrical power is given by P =
V2
Power (or heat produced) in parallel, Pp = R
p
Thus,
Ps
Pp
V2 / R s
V2 / R p
Rp
Rs
R/ 2
2R
1
4
or Ps : Pp : : 1 : 4
Thus, (C) is the correct answer.
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Page # 23
ELECTRICITY
Ex.5
How is voltmeter connected in the circuit to measure potential difference between two points?
Sol.
A voltmeter is always connected in parallel across the points between which the P.D. is to be determined.
Ex.6
A copper wire has a diameter of 0.5 mm and a resistivity of 1.6 × 10 –6 ohm cm. How much of
this wire would be required to make a 10 ohm coil? How much does the resistance change if the
diameter is doubled?
Sol.
D = 0.5 mm = 0.5 × 10 –3 m
We are given that, Diameter of the wire,
= 1.6 × 10–6 ohm cm = 1.6 × 10–8 ohm m
resistivity of copper,
required resistance, R = 10 ohm
As
R =
or
=
A
,
3. 14
4
1 0 (0 .5 1 0 –3 )2
–8
1 .6 1 0
r
Since, R =
Ex.7
R( D 2 / 4 )
RA
=
D2 / 4
D2
, R
RD 2
4
r2 =
[A =
(D/2)2 =
D2/4]
m = 112.7 m
1/D2 . When D is doubled, R becomes
1
times.
4
The values of current, I, flowing in a given resistor for the corresponding values of potential difference,
V, across the resistor are given below :
I (ampere)
:
0.5
1.0
2.0
3.0
4.0
V (volt)
:
1.6
3.4
6.7
10.2
13.2
Plot a graph between V and I and calculate the resistance of the resistor.
Sol.
The V-I graph is as shown in fig.
I (ampere)
4.0
3.0
2.65
2.0
1.25A
1.40
1.0
4V
0.5
(0,0)
1
1.6 2
3.4
5
6 6.7 7
8
9
1010.211 12 1313.2 14
V(volt)
For V = 4V (i.e., 9V – 5V), I = 1.25 A (i.e., 2.65 A – 1.40 A). Therefore, R =
V
I
4V
= 3.2
1.2 5 A
The value of R obtained from the graph depends upon the accuracy with which the graph is plotted.
Ex.8
When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in
the circuit. Find the value of the resistance of the resistor.
Sol.
Here, V = 12 V, I = 2.5 mA = 2.5 × 10 –3 A
Resistance of the resistor, R =
12V
V
=
2 .5 1 0 –3 A
I
= 4800
= 4.8 k
Ex.9
A battery of 9 V is connected in series with resistors of 0.2 , 0.3 , 0.4 , 0.5
current would flow through the 12 resistor?
Sol.
Since all the resistors are in seies, equivalent resistance,
Rs = 0.2
+ 0.3
+ 0.4
+ 0.5
V
Current through the circuit, I = R
s
9V
1 3.4
+ 12
and 12 . How much
= 13.4
0 .67 A
In series, same current (I) flows through all the resistors. Thus, current flowing through 12
= 0.67 A
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resistor
Page # 24
ELECTRICITY
Ex.10 How many 176 resistors (in parallel) are required to carry 5 A in 220 V line?
Sol.
Here, I = 5A, V = 220 V.
V
I
Resistance required in the circuit, R =
2 20 V
5A
, Resistance of each resistor, r = 176
44
If n resistors, each of resistance r, are connected in parallel to get the required resistance R, then
r
n
R =
or
44 =
17 6
n
or n =
17 6
44
= 4
Ex.11 Show how you would connect three resistors, each of resistance 6 , so that the combination has
a resistance of (i) 9 (ii) 2 .
Sol.
(i) In order to get a resistance of 9
from three resistors, each of resistance 6 , we connect two
resistors in parallel and this parallel combination (or resistance 3 ) in series with the third resistor as
shown in fig.
6
6
A
6
D
C
B
6
A
C
9
D
B
A
B
(a)
(ii) In order to get a resistance of 2 from three resistors, each of resistance 6 , we connect
all the three resistors in parallel as shown in fig (b) as equivalent resistance in parallel combination,
i.e., R p is given by Rp =
6
6
3
= 2 .
6
A
B
A
B
6
(b)
Ex.12 Several electric bulbs designed to be used on a 220 V electric supply line, are rated 10 W. How
many lamps can be connected in parallel with each other across the two wires of 220 V line if
the maximum allowable current is 5 A?
Sol.
Resistance of each bulb, r =
V2
P
Total resistance in the circuit, R
(2 20 )2
4 84 0
10
22 0 V
44
5A
Let n be the number of bulb (each of resistance r) to be connected in parallel to obtain a resistance R.
r
n
r
48 40
1 10
n = R
44
Ex.13 A hot plate of an electric oven connected to a 220 V line has two resistance coils A and B, each
of 24 resistance, which may be used separately, in series, or in parallel. What are the currents
in the three cases?
Sol.
Here, potential difference, V = 220 V
Resistance of each coil, r = 24
(i) When each of the coils A or B is connected separately, current through each foil, i.e.,
Clearly,
R =
V
or
220V
9 .2 A
I = r
24
(ii) When coils A and B are connected in series, equivalent resistance in the circuit,
Rs = r + r = 2r = 48
V
220V
4.6 A
Current through the series combination, ie.e, I s = R
48
s
(iii) When the coils A and B are connected in parallel, equivalent resistance in the circuit,
Rp =
r
2
24
2
12
Current through the parallel combination, ie.e, I p =
V
Rp
2 20 V
12
1 8.3 A
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Page # 25
ELECTRICITY
Ex.14 Compare the power used in the 2
(i) a 6 V battery in series with 1
resistor in each of the following circuits :
and 2
(ii) a 4 V battery in parallel with 12
Sol.
resistors, and
and 2
(i) Since 6 V battery is in series with 1
6V
I =
1
2
6V
3
Power used in 2
P1
Clearly, P
2
8W
8W
resistors, current in the circuit,
2A
resistor, P1 = I2R = (2A) 2 × 2
(ii) Since 4 V battery is in parallel with 12
V2
resistor, P2 =
R
Power used in 2
resistors.
and 2
and 2
(4 V)2
(2 )
= 8W
resistors, pd across 2
resistor, V = 4V.
8W
1
Ex.15 Two lamps, one rated 100 W at 220 V, and the other 60 W at 220 V, are connected in parallel
to the electric mains supply. What current is drawn from the line if the supply voltage is 220 V?
Sol.
Resistance of first lamp, r1 =
V2
P
(2 20 )2
100
resistance of the second lamp, r2 =
V2
P
4 84
(2 20 )2
60
80 6 .7
Since the two lamps are connected in parallel, the equivalent resistance is given by
1
Rp
1
r1
1
r2
r2 r 1
r2
or Rp = r
1
r2
r1
r1 r2
4 84
4 84
8 0 6.7
8 06. 7
39 04 4 2.8
12 90 .7
= 302.5
V
Current drawn from the line, i.e., I = R
p
2 20 V
30 2 .6
= 0.73 A
Ex.16 Which uses more energy, a 250 W TV set in 1 h, or a 1200 W toaster in 10 minutes?
Sol.
Energy used by 250 W TV set in 1 h = 250 W × 1h = 250 Wh
Energy used by 1200 W toaster in 10 min. (i.e., 1/6 h) = 1200 W × (1/6) h = 200 Wh
Thus, a 250 W TV set uses more power in 1 h than a 1200 W toaster in 10 minutes.
Ex.17 An electric heater of resistance 8 draws 15 A from the service mains for 2 hour. Calculate the
rate at which heat is developed in the heater.
Sol.
Here, I = 15A, R = 8 , t = 2h
Rate at which heat is developed, i.e, electric power, P = I 2 R = (15)2 × 8 = 1800 W = 1800 J/s
Ex.18 Explain the following :
(a) Why is tungsten used almost exclusively for filament of incandescent lamps?
(b) Why are the conductors of electric heating devices, such as toasters and electric irons, made
of an alloy rather than a pure metal?
(c) Why is the series arrangement not used for domestic circuits?
(d) How does the resistance of a wire vary with its cross-sectional area?
Sol.
(e) Why are copper and aluminium wires usually employed for electricity transmission.
(a) Tungsten has a high melting point (3380°C) and becomes incandescent (i.e., emits light at a
high temperature) at 2400 K.
(b) The resistivity of an alloy is generally higher than that of pure metals of which it is made of.
(c) In series arrangement, if any one of the appliances fails or is switched off, all the other appliances
stop working because the same current is passing through all the appliances.
(d) The resistance of a wire (R) varies inversely as its cross-sectional area (A) as R
1/A.
(e) Copper and Aluminium wires possess low resistivity and as such are generally used for electricity
transmission.
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ELECTRICITY
NCERT QUESTIONS WITH SOLUTIONS
Q.1
What does an electric circuit mean ?
Ans.
An electric circuit is a closed and continuous path consisting of many devices like resistors, electric
bulbs, etc. through which an electric current flows.
Q.2
Define the unit of current.
Ans.
The 51 unit of current is ampere (A). Current flowing through a conductor Is said to be 1 ampere if 1
coulomb of charge flows through it in 1 second.
Q.3
Calculate the number of electrons constituting one coulomb of charge.
Ans.
Number of electrons constituting 1 coulomb is given by,
n=
Q
, where, Q = 1 C and e = charge of a single electron = 1.6 × 10–19 C
e
or n =
1C
1.6 10
19
C
= 6.25 × 10 18 electrons.
Q.4
Name a device that helps to maintain a potential difference across a conductor.
Ans.
A battery can be used to maintain a potential difference across a conductor.
Q.5
Ans.
What is meant by saying that the potential difference between two points is 1 V ?
Potential difference between two points is 1 volt if 1 joule of work is done to carry a charge of 1
coulomb from one point to the other.
Q.6
Ans.
How much energy is given to each coulomb of charge passing through a 6V battery?
Work done, W = QV Where, Q = 1C; V = 6V W = 1C × 6V = 6J
Q.7
Ans.
On what factors does the resistance of a conductor depend?
The resistance (R) of a conductor depends upon
(i) its length ( ): R
(ii) its cross-sectional area (A): R
1
A
(iii) Nature of material i.e., resistivity ( ) of its material: R
(iv) Temperature: more the temperature, more will be its resistance.
Q.8
Ans.
Q.9
Ans.
Does current flow more easily through a thick wire or a thin wire of the same material when connected
to the same source? Why?
The current flows more easily through a thick wire than through a thin wire. This is because the
resistance R of a thick wire (large area of cross-section) is less than that of a thin wire (small area of
1
cross-section) as R
.
A
Let the resistance of an electrical component remains constant while the potential difference across
the two ends of the component decreases to half its former value. What change will occur in the
current through it?
We know that I = V/R, when potential difference becomes V/2, and resistance remains constant, then,
current becomes 1/2 of its former value.
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ELECTRICITY
Q.10
Why are coils of electric toasters and electric irons made of an alloy rather than a pure metal?
Ans.
This is because (i) resistivity of an alloy is generally higher than that of pure metals (ii) an alloy has a
high melting point and it does not oxidise at high temperatures.
Q.11
(a) which among iron and mercury is a better conductor? Given,
94.0 × 10–8 m.
iron
= 10.0 × 10–8
m and
mercury
=
(b) Which material is the best conductor?
Ans.
(a) Iron is a better conductor than mercury as resistivity ( ) for iron is less than that for mercury.
(b) Silver is the best conductor because its resistivity ( ) is least.
Q.12
Ans.
Draw a schematic diagram of a circuit consisting of a battery of three cells of 2V each, a 5 ohm
resistor, an 8 ohm resistor, and a 12 ohm resistor, and a plug key, all connected in series.
I
2V2V 2V
Q.13
k
(
Redraw the circuit of Q. 12, putting in an ammeter to measure,the current through the resistors and a
voltmeter to measure the voltage across the 12 ohm resistor. What would be the reading in the
ammeter and the voltmeter?
V
+
I
A
+
2V2V 2V
Ans.
k
(
Since all the three resistances are in series, total resistance in the circuit,
R = 5 + 8 + 12 = 25
Current in the circuit, I
V
R
2
2 2
25
6
25
0.24 A , thus, ammeter will read 0.24 A.
Potential difference across 12 ohm resistor, V = I × R = 0.24 × 12 = 2.88 V
Q.14
Judge the equivalent resistance when the following are connected in parallel (a) 1
10 3 and 106 .
and 106
(b) 1 ,
Ans.
(a) Approx. 1 (slightly less than 1 ) as other one (106 ) is very large as compared to 1 . In parallel
combination of resistors, the equivalent resistance is lesser than the least resistance (in this case, 1 ).
(b) Again, resistance is approx. 1 (slightly less than 1 ).
Q.15
An electric lamp of 100 , a toaster of resistance 50 and a water filter of resistance 500 are
connected in parallel to a 220V source. What is the resistance of an electric iron connected to the
same source that takes as much current as in three appliances and what is current through it?
Ans.
Resistance of the electric lamp, R1 = 100
R3 = 500
; resistance of toaster, R2 = 50 ; resistance of water filter,
Since R1 , R2 and R3 are connected in Parallel, their equivalent resistance (Rp ) is given by
1
Rp
1
R1
1
R2
1
R3
1
100
1
50
1
500
5 10 1
500
16
500
4
125
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Rp
125
4
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ELECTRICITY
Current through the three appliances, i.e.,
V
Rp
I
220
125 / 4
7.04 A
Since the electric iron drawing the same current when connected to the same source (220 V), its
resistance must be equal to Rp.
Thus, resistance of the electric iron,
125
4
31.25
Current through the electric iron, I = 7.04 A
Q.16
Ans.
What are the advantages of connecting electrical devices in parallel with the battery instead of
connecting them in series.
(a) In case of devices in parallel. if one device gets damaged (or open), all other will work as usual as
the whole circuit does not break. This is not with the devices connected in series because when one
device fails, the circuit breaks and all devices stop working.
(b) Since potential difference across all devices is same in parallel Circuit, they will draw required
current according to their resistances. This is not so in series circuit where same current flows through
all the devices, irrespective of their resistances.
Q.17
How can three resistors of resistances 2 , 3
(b) 1 ?
Ans.
(a) The get a total resistance of 4
as shown below.
and 6
be connected to give a total resistance of (a) 4
from resistors of resistance 2 , 3
A
and 6 , the resistors are joined
B
The resistors having resistances 3 and 6 are connected in parallel. This combination is connected in
series with the resistor of resistance 2 . Let us check it mathematically, equivalent resistance of 3
and 6 resistors is,
R1
3 6
3 6
3 6
9
Now, R1 and 2
2
resistors are in series, their equivalent resistance is Re = R1 + 2 = 2 + 2 = 4 .
(b) To get a resistance of 1
below.
from three given resistors of resistance 2 , 3 , 6 , are joined as shown
A
B
They all are connected in parallel. Their equivalent resistance is given by,
1
R
1
2
1
3
1
6
3
2
6
1
6
6
1
R=
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ELECTRICITY
Q.18
What is (a) the highest, (b) the lowest total resistance that can be secured by combinations of four
coils of resistance 4 , 8 , 12 , 24 ?
Ans.
(a) The highest resistance is secured when all the resistors are connected in series. The equivalent
resistance is given by,
Re = 4
+8
+ 12
+ 24
= 48 .
(b) The lowest resistance is secured when all the four coils are connected in parallel. The equivalent
resistance is given by,
1
Re
1
4
1
8
1
12
1
24
6
3 2
24
1
12
24
1
2
or Re = 2
Q.19
Why does the cord of electric heater not glow while the heating element does?
Ans.
The cord of an electric heater is made of thick copper wire and has much lower resistance than the
heating element. For the same current (I) flowing through the cord and the element, heat produced in
the element is much more than that produced in the cord. As a result, the element becomes very hot
and glows whereas the cord does not become hot and as such does not glow.
Q.20
Compute the heat generated while transferring 96000 coulombs of charge in one hour through a
potential difference of 50 V.
Ans.
Here, charge, Q = 96000C; time, t = 1 hr
potential difference, V = 50V.
Heat produced, H = V I t = V × q
[ q = I t]
= 96000C × 50V = 4.8 × 106 J.
Q.21
An electric iron of resistance 20
takes a current of 5A. Calculate the heat developed in 30s.
Ans.
Here, resistance, R = 20 , current, I = 5A, time, t = 30 s.
Heat produced, H = I2 R t = (5)2 5 20 × 30 = 1.5 × 104 J.
Q.22
What determines the rate at which energy is delivered by a current?
Ans.
Electric power determines the rate at which energy is delivered by a current.
Q.23
An electric motor takes 5A from a 220V. Determine the power and energy consumed in 2Hr.
Ans.
Here, current, I = 5A; potential difference, V = 220V; time, t = 2hr = 2 × 60 × 60 = 72000
= 7.92 × 10 6 J
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ELECTRICITY
EXERCISE – I
BOARD PROBLEMS
Q.1
Define resistivity of a material.
[2004]
Q.2
A cylinder of a material is 10 cm long and has
Q.14
connecting domestic electrical appliances in a
circuit ?
a cross-section of 2 cm2. If its resistance along
the length be 20 , what will be its resistivity
in number and units.
Q.3
filaments of incandescent lamps ?
Q.4
Q.15
[2004]
Why is tungsten metal selected for making
Why is series arrangement not used for
Out of 60 W and 40 W lamps, which one has a
higher resistance when in use?
Q.16
[2005]
An electric bulb draws a current of 0·2 A when
of charge flowing through it in one hour.
[2004]
closed circle. What is the effective resistance
diameter of this circle?
Q.5
A wire of resistance 5
[2005]
Q.17
is bent in the form of a
circle ?
Q.6
A wire of resistance 20
[2005]
An electric iron draws a current of 0·5 A when
the voltage is 200 volts. Calculate the amount
of electric charge flowing through it in one
closed circle. What is the resistance between
two points at the ends of any diameter of the
[2008]
the voltage is 220 volts. Calculate the amount
A resistance of 10 ohm is bent in the form of a
between the two points at the ends of any
[2008]
hour.
Q.18
[2004]
An electric appliance draws a current of 0·4 A
when the voltage is 200 volts. Calculate the
is bent in the form of
amount of charge flowing through it in one
a closed circle. What is the effective resistance
hour.
[2004]
between the two points at the ends of any
diameter of the circle?
Q.7
[2005]
Q.19
flow in 1 hour through the element of an electric
Why is much less heat generated in long electric
bulb drawing a current of 0·2 A.
cables than in filaments of electric bulbs?
[2005]
Q.8
Calculate the amount of charge that would
Q.20
Calculate the amount of charge that would
flow in 2 hours through the element of an
State which has a higher resistance: a 50 W
electric bulb drawing a current of 0·25 A.
or a 25 W lamp bulb and how many times?
[2004]
[2005]
Q.9
What is the power of torch bulb rated at 2·5 V
and 500 mA ?
Q.21
Calculate the amount of charge that would
flow in 1 hour through the element of an electric
[2005]
iron drawing a current of 0·4 A.
Q.10
Q.22
Out of the two, a toaster of 1 kW and an
Q.23
electric heater of 2 kW, which has a greater
resistance?
[2006]
10
[2007]
and
are connected in series, how does the
current passing through the two resistors
compare ?
What is meant by the statement "Potential
electric circuit is 1 volt ?
[2006]
(ii) In a circuit if the two resistors of 5
What is the SI unit of electrical potential ?
difference between two points A and B in an
[2005]
(i) Draw a circuit diagram to show how two
resistors are connected in series.
[2007]
Q.13
Derive the relation R = R1 + R 2 + R 3 when
resistors are joined in series.
one of them has higher resistance ? [2006]
Q.12
[2004]
There are two electric bulbs, (i) marked 60 W,
220 V and (ii) marked 100 W ; 220 V. Which
Q.11
[2004]
Q.24
A bulb is rated at 5.0 V, 100 mA. Calculate its
(i) power and (ii) resistance.
[2006]
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ELECTRICITY
Q.25
An electric iron has a rating of 750 W, 220 V.
Calculate
Q.31
(i) State the formula showing how the current
[2007]
I in a conductor varies when the potential
difference V applied across it is increased
(i) current passing through it, and
stepwise
(ii) its resistance, when in use.
Q.26
(ii) Show this relationship also on a schematic
An electric lamp is marked 100 W, 220 V. It is
used for 5 hours daily. Calculate
graph.
[2007]
(iii) Calculate the resistance of a conductor if
(i) its resistance while glowing
the current flowing through it is 0·2 ampere
when the applied potential difference is 0·8
(ii) energy consumed in kWh per day.
Q.27
[2004]
volt.
Three resistors are connected as shown in Fig.
Through a resistor of 5 ohm, a current of 1
ampere is flowing.
Q.32
A torch bulb is rated 5·0 V and 500 mA.
Calculate its (i) power (ii) resistance and (iii)
[2003]
energy consumed when it is lighted for 4 hours.
[2005]
I2 R2= 10
I1
I1 R1= 5
A
B
I1
I3 R2= 15
Q.33
If a 12 V ba tt ery i s co nnec ted to t he
arrangement of resistances given in Fig. (with
C
5
replaced by 10
and 10
, 15
replaced by 25
replaced by 5
). Calculate (i) the
(a) What is the potential difference across AB
total effective resistance of the arrangement
and across AC ?
and (ii) the total current flowing in the circuit.
[2005]
(b) What is the current through the other two
resistors ?
5
20
15
10
(c) What is the total resistance?
Q.28
An electric bulb is rated at 200 V-100 W. What
I
I
is its resistance? Five such bulbs burn for 4
hours. What is electrical energy consumed ?
( )
24V
Calculate the cost if the rate is 50 paise unit.
[2003]
Q.29
Q.34
Two electric lamps of 100 W and 25 W
respectively are joined in parallel to a supply
State the formula co-relating the electric
of 200 V. Calculate the total current flowing
current flowing in a conductor and the voltage
through the circuit.
[2005]
applied across it. Also show this relationship
Q.35
by drawing a graph.
Two identical resistors, each of resistance 2
, are connected in turn (i) in series, and (ii)
What would be the resistance of a conductor
in parallel, to a battery of 12 V. Calculate the
if the current flowing through it is 0·35 ampere
ratio of power consumed in the two cases.
when the potential difference across it is 1·4
volt.
[2005]
[2004]
Q.36
Q.30
When a potential difference of 1·2 volt is applied
Two identical resistors, each of resistance 10
are connected in (i) series, and (ii) in parallel,
across a conductor, the current flowing through
in turn to a battery of 10 V. Calculate the ratio
it is 0·25 ampere. Calculate the resistance of
of power consumed in the combination of
the conductor.
resistors in the two cases.
[2004]
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[2005]
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Q.37
ELECTRICITY
In the given cir cuit , ca lculate (i ) t ota l
Q.42
resistance of the circuit, and (ii) current shown
by the ammeter.
for studying Ohm's law.
Q.43
R1=3
Two lamps, one rated 60 W at 220 V and the
other 40 W at 220 V, are connected in parallel
to the electric supply at 220 V.
R2=2
Q
+
A
[2007]
(b) Draw a schematic diagram of the circuit
[2005]
R3 = 5
P
(a) State Ohm's law.
[2008]
(a) Draw a ci rcuit diagram to show the
–
connections.
2.5V
(b) Calculate the current drawn from the
electric supply.
Q.38
(i) Draw a schematic diagram of a circuit
(c) Calculate the total energy consumed by
consisting of a battery of five 2 V cells, a 5
resistor, a 10
resistor and a 15
the two lamps together when they operate for
resistor,
one hour.
and a plug key, all connected in series. [2006]
(ii) Calculate the current passing through the
Q.44
and 'short-circuiting' as used in domestic
above circuit when key is closed.
Q.39
circuits.
In a household, 5 tube lights of 40 W each are
of an alloy than a pure metal ?
W for 4 hour each day. Calculate the total
energy consumed by the tube lights and press
Q.40
Q.45
[2006]
resistance
total resistance in arm CE, (b) total current
I1
A
D 4
2
[2008]
(b) the total current in the circuit
drawn from the battery, and (c) current in each
C
For the circuit shown in Fig., calculate
(a ) t he value o f cu rrent t hrough ea ch
In the circuit shown in Fig., calculate : (a)
arm, i.e., AB and CE of the circuit.
[2008]
(b) Why are the coils of electric toasters made
used for 5 hours and an electric press of 500
in a month of 30 days.
(a) Distinguish between the terms 'overloading'
(c) the total effective resistance of the circuit.
[2006]
I2
6
I2
B
+
( )
5
I1
E
I
–
I3
10
30
I
–
3V
( )
A
+
6V
Q.41
(a) What is meant by 'Electric Resistance' of a
conductor?
[2007]
(b) A wire of length L and resistance R is
stretched so that its length is doubled and
area of cross· section is halved. How will its :
(i) resistance change ?
(ii) resistivity change ?
Q.46
(a) Express Ohm's law by a mathematical
formula.
[2004]
(b) Draw a circuit diagram to verify Ohm's law.
(c) Present the relationship between the
voltage applied across a conductor and the
current flowing through it graphically.
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ELECTRICITY
Q.47
State Ohm's law. Express it mathematically.
(a) Name an instrument that measures electric
Define SI uni t of resistance. Derive an
current in a circuit. Define the unit of electric
expression for the equivalent resistance of three
current.
resistors R1 , R2 and R3 connected in series (or
(b) What do the following symbols mean in
in parallel).
Q.48
Q.50
[2004]
[2008]
circuit diagram ?
(a) Express Ohm's law both by a mathematical
formula and by a graph line.
[2004]
V (volt)
(b) State SI units of
(i) resistance and
1.6
1.5
(ii) resistivity.
1.2
1.0
0.8
0.5
(c) What will be the equivalent resistance of
two resistors R1 and R2
0
0.1 0.2 0.3 0.4
0.5 0.6
I(A)
(i) connected in series and
(ii) connected in parallel.
Q.49
(a) What is meant by saying that the potential
difference between two points is 1 volt? Name
(i)
(ii)
( )
a device that helps to measure the potential
difference across a conductor.
[2008]
(b) Why does the connecting cord of an electric
heater not glow hot while the heating element
does ?
(c) Electrical resistivities of some substances
at 20°C are given below:
(c) An electric circuit consisting of a 0·5 m
long nichrome wire XY, an ammeter, a voltmeter,
four cells of 1·5 V each and a plug key was set
up.
(i) Draw a diagram of this electric circuit to
study the relation between the potential
difference maintained between the points 'X'
Silver
1·60 × 10–8
m
Copper
1·62 × 10–8
m
Tungsten
5·20 × 10–8
m
Iron
10·0 × 10–8
m
Mercury
94·0 × 10–8
m
Nichrome
100 × 10–6
m
and 'Y' and the electric current flowing through
XY.
(ii) Graph shown in Fig. was plotted between
V and I values.
What would be the values of V/I ratios when
the potential difference is 0·8 V, 1·2 V and 1·6
V respectively? What conclusion do you draw
from these values ?
Answer the following questions in relation to
them :
(i) Among silver and copper, which one is a
better conductor? Why ?
(ii) Which material would you advise to be used
in electrical heating devices ? Why ?
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ELECTRICITY
EXERCISE – II
Q.1
OLYMPIAD QUESTIONS
If a charged body attracts another body,
the charge on the other body :(A) must be negative
(B) must be positive
(C) must be zero
(D) may be negative or positive or zero
Q.2
1 MeV is equal to :(A) 1.6 × 10 –19 J (B) 1.6 × 10 –14 J
(C) 1.6 × 10 –13 J (D) 1.6 × 10 +13 J
Q.3
Q.4
Q.5
1
A man has five resistors each of value
.
5
What is the maximum resistance he can
obtain by connecting them ?
(A) 1
(B) 5
2
1
(C)
(D)
5
2
Materials which allow larger currents to flow
through them are called :-
(A) 106 A
(C) 10 –3 A
(B) 10 –6 A
(D) 10 A
Q.12 How many electrons constitute a current of
one microampere?
(A) 6.25 × 10 6
(C) 6.25 x 10 9
(B) 6.25 × 10 12
(D) 6.25 × 10 15
Q.13 The SI unit of specific resistance is :(A) ohm m
(C) ohm m 2
(B) ohm m –1
(D) (ohm) –1
Q.14 T he e ffe ct i ve re si st a nce of a c ir cu it
containing resistances in parallel is (A) equal to the sum of t he individua l
resistances
(C ) gr eat er t han a ny o f t he indi vi dua l
resistances
(B) Ite
(D) It/e
Conventionally, the direction of the current
is taken as -
(C) the direction of flow of molecules
(D) the direction of flow of positive charge
The unit of specific resistance is :(A) ohm
(C) ohm-metre
(B) mho
(d) ohm per metre
1 volt equals :(A) 1 joule
(B) 1 joule per coulomb
(C) 1 coulomb per metre
(D) 1 newton per coulomb
Q.9
Q.11 One ampere equals :-
If I is the current through a wire and e is
the charge of electrons, then the number
of electrons in t seconds will be given
by :-
(A) the direction of flow to negative charge
(B) the direction of flow of atoms
Q.8
(B) molecules
(D) electrons
(B) s ma ller than any of t he individua l
resistances
Ie
t
(C) e/It
Q.7
(A) atoms
(C) protons
(A) Insulators
(B) Conductors
(C) Semiconductors(D) Alloys
(A)
Q.6
Q.10 Good conductors have many loosely bound-
The reciprocal of resistance is conductance.
If the unit of resistance is ohm, the unit
of conductance will be (A) ohm
(C) mho
(B) volt
(D) ohm metre –1
(D) sometimes greater and sometimes smaller
than the individual resistances
Q.15 Electric field intensity is
(A) a scalar quantity
(B) a vector quantity
(C) neither scalar nor vector
(D) sometimes scalar and sometimes vector
Q.16 Electric potential is
(A) A scalar quantity
(B) a vector quantity
(C) neither scalar nor vector
(D) sometimes scalar and sometimes vector
Q.17 In Co ul o mb' s l a w, t he c on st a nt
proportionality k has the units (A) N
(C) NC2/m2
of
(B) Nm2
(D) Nm2/C 2
Q.18 The variable resistance is called :(A) resistor
(C) open switch
(B) rheostat
(D) none of these
Q.19 The law that governs the force between
electric charges is called (A) Ampere's law
(C) Faraday's law
(B) Coulomb's law
(D) Ohm's law
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ELECTRICITY
Q.20 A charge q is placed at the center of the
line joining two equal charges Q. The system
of the three charges will be in equilibrium,
if q is equal to Q
Q
(B) –
2
4
Q
Q
(C) +
(D) +
4
2
Q.21 The force between two electrons separated
by a distance r varies as :(A)
(A) r 2
(C) r –1
(B) r
(D) r–2
Q.22 When the distance between the charged
particles is halved, the force between them
becomes (A) One-fourth
(C) Double
(B) Half
(D) Four times
Q.23 A charge q 1 exerts some force on a second
charge q 2. If third charge q 3 is brought near,
the force of q 1 exerted on, q 2 : (A) Decreases
(B) Increases
(C) Remains unchanged
(D) Increases if q 3 is of the same sign as
q 1 and decreases if q 3 is of opposite sign
Q.24 If the charge is moved against the coulomb
force of an electric field (A) Work is done by the electric field
(B) Energy is used from some outside force
(C) The strength of the field is decreased
(D) The energy of the system is decreased
Q.25 The ratio of the forces between two small
spheres with constant charge (a) in air (b)
in a medium of dielectric constant K is(A) 1 : K
(C) 1 : K 2
(B) K : 1
(D) K 2 : 1
Q.26 Two charges are placed at a distance. If a
glass slab is placed between them, force
between them will be
(A) Zero
(C) Decreased
(8) Increased
(D) Remains same
Q.27 If a unit positive charge is taken from one
point t o a no ther over an e quipot entia l
surface, then (A) Work is done on the charge
(B) Work is done by the charge
(C) Work done is constant
(D) No work is done
Q.28 If a glass rod is rubbed with silk, it acquires
a positive charge because(A) Protons are added to it
(C) Electrons are added to it
(B) Protons are removed from it
(D) Electrons are removed from it
Q.29 Two resistors of resistance R 1 and R2 having
R1 > R 2 are co nnecte d i n pa rallel. For
e qui va l e nt r e si st a nc e R , t he co rr e ct
statement is (A) R > R 1 + R 2
(B) R 1 < R < R 2
(C) R2 < R < (R1 + R2)
(D) R < R1
Q.30 Two unequal resistances are connected in
parallel. Which one of the statement is
correct(A) The current flowing is same in both
(B) M ore cur rent wi ll flow from higher
resistance piece
(C) The potential drop is same in both
(D) The conductivity of lower resistance is
less
Q.31 There are 8 equal resistances R. Two are
connected in parallel, such four groups are
connected in series, the total resistance
(A) R/2
(C) 4R
(B) 2R
(D) 8R
Q.32 In a conductor 4 coulombs of charge flows
for 2 seconds. The value of electric current
will be(A) 4V
(C) 2A
(B) 4A
(D) 2V
Q.33 In a conductor, the flow of current is :(A) Flow of molecules
(B) Flow of free electrons
(C) Flow of positive charge
(D) Flow of ions
Q.34 Three resistances of magnitude 2, 3 and 5
ohm are connected in parallel to a battery
of 10 volts and of negligible resistance. The
potential difference across 3 resistance will
be(A) 2V
(C) 5V
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ELECTRICITY
Q.35 In the circuit shown below, the ammeter A
reads 5A and the voltmeter V reads 20 V
(Fig.). The correct value of resistance R is:-
Q.39 What is the resistance between A and B in
the given network (Fig.) ?
1
1
R
A
A
B
2
V
(A) exactly 4
(B) slightly greater than 4
(C) slightly less than 4
(D) zero
Q.36 What is the current in the circuit shown (Fig.)
2
(A) 2
(B) 2
2
3
(C)
(D)
3
2
Q.40 The equivalent resistance between A and B
(Fig.) will be :1
A
2
2
2
2
2
B
2
I
2V
(A) 1.5 A
(B) 0.5 A
(C) 2.5 A
(D) none of these
Q.37 In the circuit shown in Fig., the reading of
the voltmeter V will be :-
(A) 7
(B) 2
5
(C)
(D) 1
3
Q.41 What is the resistance between A and B ?
2
2
12V
2
2
–
+
2
A
100
2
V
(A) 4V
(B) 2V
(C) 6V
(D) 3V
Q.38 Which of the following networks yields maximum
effective resistance between A and B?
B
4
3
(A)
(B)
3
4
16
(C)
(D) infinity
3
Q.42 The slope of voltage (V) versus current (I)
is called :Y
2
2
(A)
A
V
B
O
2
2
2
X
i
(B)
A
B
2
2V
2
(C)
I
(A) resistance
(B) conductance
(C) resistivity
(D) conductivity
Q.43 The current in the adjoining circuit will be-
A
30
30
B
2
30
2
2
(A)
1
A
45
(B)
1
A
15
(C)
1
A
10
(D)
1
A
5
2
B
(D) A
2
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ELECTRICITY
Q.44 The resistance wires are made of the material
Q.50 The cost of electricity is about 30 paise per
having :-
unit for household use. This unit is the same
( A) L ow spe ci fi c r e si st a nc e a nd l o w
as
temperature coefficient of resistance.
(A) ohm
(B) ampere
( B) Hi gh spe ci fi c re si st a nce an d l o w
(C) volt
(D) kilowatt-hour
temperature coefficient of resistance.
( C) Lo w sp ec i fic r e si st a nce a nd hi gh
temperature coefficient of resistance.
Q.51 A fuse wire should have
(A) low resistance and low melting point
(B) low resistance and high melting point.
( D) H igh spe ci fi c r esi st a nce a nd hi gh
temperature coefficient of resistance.
Q.45 The resistance between points A and B in
(C) high resistance and low melting point.
(D) high resistance and high melting point.
Q.52 A o ne- o hm an d ha lf- o hm res ist o r a re
Fig. is :-
connected in parallel across a 3 volt battery.
R
Total energy given out per second is
R
R
R
(A) 27 J
(C) 4.5 J
R
(A)
7
R
3
(C) 5R
(B) 3R
(D)
4
R
3
Q.46 Two wires of same material and same mass
have their lengths in the ratio 1 : 2. Their
electrical resistances are in the ratio
(A) 1 : 1
(B) 1: 2
(C) 2: 1
(D) 1: 4
Q.47 A 24 V potential difference is applied across
(B) 9 J
(D) 3 J
Q.53 Two electric lamps each of 100 watts 220
V are connected in series to a supply of 220
volts. The power consumed would be
(A) 100 watts
(B) 200 watts
(C) 25 watts
(D) 50 watts
Q.54 A rheostat can be used in an electrical circuit
as a
(A) standard resistance
(B) potential divider
(C) heat controller
a parallel combination of four 6-ohm resistors.
The current in each resistor is
(A) 1A
(B) 4A
(C) 16 A
(D) 36 A
(D) on-off switch
Q.55 The potential difference between points A
and B of adjoining figure is
Q.48 Three resistors in parallel have an effective
re s is t anc e of 1 o hm. Wh en t he y a re
A
B
5
connected in series their resistance is 9 ohm.
The resistance of each resistor is :
A 4, 4, 1 ohm
(B) 6, 2, 1 ohm
(C) 3, 3, 3 ohm
(D) 2, 3, 4 ohm
2V
5
5
D
5
5
5
C
Q.49 Fo ur 20 o hm r es ist o rs a re co nne ct e d
together to form a square. The resistance
(A)
2
V
3
(B)
(C)
4
V
3
(D) 2 V
between opposite corners will be :(A) 20 ohm
(C) 24 ohm
(B) 22 ohm
(D) 24.8 ohm
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V
9
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ELECTRICITY
Q.56 the value of equivalent resistance between
Q.59 Eight ident ical spherical mercury drops
the points A and B in the given circuit, will
be
[NTSE]
charged to a pot ential of 20V each are
coalesced into a single spherical drop
R
R
[NTSE]
A
(A) the internal energy of the system remains
the same
R
R
(B) the new potential of the drop is 80V
(C) internal energy of the system decreases
B
R
R
(D) the potential remains the same i.e. 20V
(A) 6 R
(B)
4R
11
11R
4
(D)
R
6
(C)
Q.60 A t e chni cia n has 10 r esi st ors e ach o f
resistance 0.1 . The largest and smallest
resistance that he can obtain by combining
these resistors are
(A) 10
and 1
Q.57 Consider a simple circuit containing a battery
(B) 1
and 0.1
and three identical incandescent bulbs A, B
and C. Bulb A is wired in parallel with bulb
B and this combination is wired in series with
bulb C. What would happen to the brightness
of the other two bulbs if bulb A were to
(C) 1
and 0.01
burn out?
[NTSE]
C
A
B
I
(D) 0.1
[NTSE]
respectively
respectively
respectively
and 0.01
respectively
ANSWER KEY
1.
D
2.
C
3.
A
4.
B
5.
D
6.
D
7.
C
8.
B
9.
C
10.
D
11.
A
12.
B
13.
A
14.
B
15.
B
16.
A
17.
D
18.
B
19.
B
20.
B
21.
D
22.
D
23.
C
24.
B
25.
B
26.
D
27.
D
28.
D
29.
D
30.
C
31.
B
32.
C
33.
B
34.
D
35.
B
36.
A
37.
A
38.
A
39.
D
40.
D
41.
C
42.
A
43.
C
44.
B
45.
A
46.
D
47.
B
48.
C
49.
A
50.
D
51.
A
52.
A
53.
D
54.
B
55.
C
56.
C
57.
C
58.
C
59.
B
60.
C
V
(A) Only bulb B would get brighter
(B) Both A and B would get brighter
(C) Bulb B would get brighter and bulb C
would get dimmer
( D) The re w ould b e no c hange in the
brightness of either bulb B or bulb C.
Q.58 Three equal resistors connected in series
across a source of emf dissipates 10 watts
of power. What will be the power dissipated
is watts if the same resistors are connected
in parallel across the same source of emf?
(A) 10W
(B) 30W
(C) 90W
(D)
10
W
3
[NTSE]
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CHEMICAL REACTIONS AND EQUATIONS
Page # 39
CHEMICAL REACTIONS AND EQUATIONS
INTRODUCTION
We observe many chemical changes taking place in our daily life. The milk turns sour if kept for a long
time at room temperature, milk changes to curd, rusting of iron, digestion of food in our body are
examples of chemical changes.
In such changes, the nature and the properties of the substances change and we say a chemical
reaction has taken place.
A chemical reaction is represented by a chemical equation which is a convenient way of describing a
chemical reaction with the help of symbols of elements and formulae of chemical compounds.
In this chapter, we shall discuss about chemical formulae, chemical equations, balancing of chemical
equations and types of chemical reactions.
Physical change :– A change in which the physical properties of the substance changes but the
chemical composition does not change. The substance is restored to its original state as soon as the
cause of change is withdrawn.
Chemical change :– In a chemical change, at least one of the reacting substance changes into a new
substances with a different composition. The new substances can not be changed back to the original
substance even if the cause of change is withdrawn.
DIFFERENCE BETWEEN PHYSICAL & CHEMICAL CHANGE
S.No.
Physical change
Chemical change
1
The ident it y of the substance is The ident it y of the original
maintained.
substance is completely lost.
2
The change is temporary, the
The change is permanent.
substance returns to its original
st ate as the cause of. change
is withdrawn
3
No new substance is produced. A new substance is always
produced.
4
Heat change may or may not
occur.
5
Only the physical state or some The substance after t he change
of the physical properties of the can not come back to its original
substances are changed
state even when the cause of
change is withdrawn.
6
Eg. Iron t awa is left exposed t o Eg. Ferment ation of rice, breathing,
air, melting of wax.
curding of milk.
Heat change may occur.
CHEMICAL REACTION
The processes, in which a substance or substances undergo a chemical change to produce new substance
or substances, with entire new properties, are known as chemical reaction.
The nature and identity of products totally changes from the reactants.
Some important characteristics of chemical reactions are:
(i)
Change in state: The physical state of the substances normally changes.
e.g
(a) Formation of solid MgO from solid Mg and gaseous O 2.
(b) Formation of solid Pbl(ppt) from liquid solutions of PbNO 3 and Kl.
(c) Formation of H2 gas from the reaction of solid Zn with liquid H2SO 4.
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(ii)
CHEMICAL REACTIONS AND EQUATIONS
Change in colour : In some of the chemical reactions change in colour can be observed.
e.g.
(a) Formation of brown rust on black iron nails.
(b) Formation of yellow ppt. of lead iodide from colourless solution of PbNO3 and Kl.
(iii)
Evolution on a gas: In some cases, a gas may be evolved.
e.g.
(a) Evolution of H2 gas, in the reaction between Zn and dil HCL
(b) Evolution of CO2 gas, during burning of any fuel, which contains carbon.
(iv)
Change in temperature: Most of the reactions are accompanied by temperature change. i.e.
increase or decrease in temperature.
e.g.
(a) In the reaction between Zn and H 2 SO4 , flask was found to be warm. Thus rise in
temperature has taken place.
(b) If a reaction between barium hydroxide, Ba(OH)2 and ammonium chloride, NH4 Cl is carried
out in a test tube, it is observed that bottom of test tube becomes cooler.
Q.
Check Your Concepts
From the given exaples, identify the chemical changes.
(a) Fermentation of grapes.
(b) Burning of a candle.
(c) Evaporation of alcohol.
(d) Freezing of water.
(e) Turning brown of a freshly cut apple in the air.
(f) Growth of a plant.
(g) Dissolution of sugar in water.
(h) Fading of coloured clothes in the sun.
WORD EQUATION
A chemical equation which represents a chemical reaction briefly in words is called word equation.
Example : For the example the word equation is
Sodium + water
Sodium hydroxide + Hydrogen
Do You Know?
Reactants:- The substance or substances which takes part in a chemical reaction are
called reactants.
Products:- The new substance or substances formed as a result of a chemical reaction
are called products.
In the above reaction sodium & water are reactants and sodium hydroxide & hydrogen are products.
RULES FOR WRITING A WORD EQUATION
(i) The substances taking part in chemical reaction, reactants are always written on the left hand side
of arrow.
(ii) The substances formed after the chemical reaction, products are always written on the right hand
side of arrow.
(iii) A plus sign (+) is put in between the reactants or between the products. If their number is two or
more.
(iv) An arrow (
) is put between the reactants and products, the arrow shows the direction of the
reaction in which the reaction proceeds. The arrow is read as "to yield" or "to form".
In the word equation when symbols and chemical formulae of the reactants and products are
used then it is called as chemical equation.
Example :
Na + H2O
NaOH + H2
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CHEMICAL REACTIONS AND EQUATIONS
Page # 41
IMPORTANT TERMS AND CONCEPTS
I.
Formulae of Ions
1.
Valency. The number of electrons shared by an atom is called its valency. It is also called the
combining capacity of an atom, e.g., Cl atom can share one valence electron, its valency is 1, Oxygen
can share two valence electrons, its valency is 2. Nitrogen can share 3 valence electrons, its valency
is 3, Carbon can share 4 valence electrons, therefore its valency is 4 and so on.
It means if Carbon combines with Chlorine, Carbon will share four valence electrons with four Chlorine
atoms, therefore the molecular formula of the covalent compound will be
i.e. CCl4 is formula.
Some more examples are :
+ 1 Charge
Formula
+ 2 Charge
Chromium (III) ion
Potassium ion
Manganese (II) ion
Au
1 Charge
Name of ion
Bromide ion
Chloride ion
Fl uoride ion
Iodide ion
Sb3+
Hg 2+
2
+
Formula
Br
Cl
F
I
2 Charge
Name of ion
Oxide ion
Sulphide ion
Formula
O2
S2
3 Charge
Name of ion
Nitride ion
Phosphide ion
Boride ion
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N3
P3
B3
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CHEMICAL REACTIONS AND EQUATIONS
*The elements show more than one valency. So a Roman numeral shows theft valency in a bracket.
1 Charge
Formula
Name of ion
Hydrogen carbonate
2 Charge
Name of ion
CO23
HCO3
HSO4
Manganate ion
O 24
Thiosulphate ion
2
3
O
Phosphate ion
O34
O33
O32
NO3
O 24
ClO3
Phosphite ion
O24
MnO4
O72
O 33
O 33
O32
NO2
O 34
Ferricyanide ion
- 4 Charge
O24
O24
PO2
AlO2
[Fe(CN)6]
–4
+1 Charge
NH+4
2.
Chemical Equations. “A chemical equation is a symbolic notation that uses formulae of compounds
and symbols of elements to represent a chemical reaction”, e.g., Copper oxide reacts with Carbon to
form Copper and Carbon monoxide. The reaction may be represented as
CuO + C
3.
Cu + Co
Writing of a Chemical Equation.
(i) The symbols of elements and the formulae of reacting substances (reactants) are written on the
left hand side and plus (+) sign is written between them.
(ii) The symbols and formulae of the substances formed (products) are written on the right hand side
with a plus sign (+) between them.
(iii) An arrow (
) sign in put between the reactants and products, e. g.,,
Mg + H2 SO4
MgSO4 + H2
(iv) The physical states of the reactants and products are also mentioned in a chemical equation.
The notations g, l, s, aq. are written in brackets along with symbols/formulae of reactants and products.
These symbols stand for gaseous, liquid, solid and aqueous solution respectively, e.g.,
Mg (s) + H2 SO4 (aq)
MgSO4 (aq) + H2 (g)
Zn (s) + H2 SO4 (aq)
ZnSO4 (aq) + H2
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CHEMICAL REACTIONS AND EQUATIONS
Page # 43
The symbol ( ) may also be used to represent a gaseous product. The symbol ( ) is used to
represent the formation of a precipitate (water insoluble) or a sparingly soluble substance formed
during the reaction which settles down mostly, e.g.,
NaCl (aq) + AgNO3 (aq)
AgCl ( ) + NaNO3 (aq)
(v) Sometimes, the temperature, pressure and catalyst of the reaction are indicated above and or
below the arrow in the equation, e.g.,
CO (g) + 2H2 (g)
ZnO / Cr2O3
340 atm, heat
CH3 OH (g)
(vi) A chemical equation represents an actual chemical reaction in which the reactants and products
are known, e.g.,
2 KMnO4 (s)
2 KClO3 (s)
4.
heat
heat
MnO2
K2 MnO4 (s) + MnO2 (s) + O2 (g)
2 KCl (s) + 3 O2 (g)
Balancing of chemical equation. Observe the following two chemical equations :
Zn + H2 SO4
Na + H2 O
ZnSO4 + H2
NaOH + H2
……(i)
…….(ii)
In equation (i), the number of atoms of Zn, H, S, and O are equal on both sides, i.e., the equation is
balanced.
5.
Balanced Equations. The equations in which atoms of various elements on the reactant’s and the
product’s side are equal.
Equation (ii) is not balanced because the number of hydrogen atoms is not equal on both
sides. It is called a skeleton chemical equation.
6.
Reason of Balancing Equat ions. The number of atoms of elements on both sides of a chemical
equation should be equal in accordance with the law of conservation of mass.
7.
Balancing. The process of making atoms of various elements equal in an equation on either side is
called balancing.
8.
Steps in Balancing of Chemical Equations. A number of steps are involved in balancing a chemical
equation, e.g.,
Na + H2 O
NaOH + H2
Step 1: Examine the number of atoms of different elements present in unbalanced equation.
Number of atoms in
reactants
Step 2: Pick an element to balance the equation. In the above equation Na and O are balanced, Hydrogen is
not.
Step : To balance Hydrogen on both sides we need to multiply H2O by 2 which makes Hydrogen atoms equal to
4 on the reactants’ side. To make Hydrogen 4 on the products’ side, multiply NaOH by 2. Now oxygen
has become 2 on both sides. But Sodium atom has become two on the product’s side. Multiply Na by 2
on the reactant’s side so that they become equal on both sides. The steps are as follows :
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CHEMICAL REACTIONS AND EQUATIONS
(i)
Na + 2H2 O
(ii)
Na + 2 H2 O
(iii)
2 Na + 2 H2 O
NaOH + H2
2 NaOH + H2
2 NaOH + H2
The equation is now balanced.
Example : Fe + H2O
Step 1 :
Element
Fe3O4 + H2
Number of atoms in
reactants
Step 2 : Pick up the compound which has the maximum number of atoms whether a reactant or a product,
and in that compound select the element which has the highest number of atoms, e.g., we select
Fe 3O4 in the above equation :
To balance oxygen atoms,
In reactant
To equalise the number of atoms, we put the coefficient on the left side of the formula. A coefficient is
a small whole number, like coefficients used in algebraic equations. You must keep in mind that we can
put coefficients but we cannot change the subscripts in the formula, i.e., to balance Oxygen atoms,
we can put the coefficient 4 as 4 H 2O and not H2O 4 or (H2 O)4 . Now the partly balanced equation
becomes as follows :
Fe (s) + 4 H2O (g)
Fe 3O4 (s) + H2 (g)
(Partly balanced)
Step 3 : Pick up the second element to balance this partly balanced equation. Let us try to balance hydrogen
atoms. bIn partly balanced equation. Atoms of Hydrogen
To equalise the number of Hydrogen atoms, we use 4 as the coefficient of H 2 in the products.
Fe (s) + 4H2 O (g)
Fe3 O4 (s) 4H2
Step 4 : Pick up the third element to be balanced. The element which is left to be balanced is Fe.
Atoms of Iron
To equalise iron, we use 3 as coefficient of Fe in reactants.
3 Fe + 4 H2O
Fe3O4 + 4H2
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CHEMICAL REACTIONS AND EQUATIONS
Page # 45
Step 5 : Check the correctness of the balanced equation.
Atoms
The equation is balanced because atoms of all the elements are equal on both sides. This method of
balancing equation is known as hit and trial method.
9.
Balancing of Ionic Equations. In these equations, charge balancing is also done along with balancing
of atoms on both sides of the equation, e.g.,
Initial
Cu2+ (aq) + H2 S
Balanced Cu2+ (aq) + H2S
CuS (s) + H+ (aq).
CuS (s) + 2 H+ (aq)
We have balanced the charges. It was + 2 on LHS and we have made + 2 on RHS. Number of Hydrogen
atoms, Cu and Sulphur atoms are also balanced on both sides.
Do You Know?
A chemical equation that conserves the amounts of all
elements and electrical charges, is said to be balanced.
Q.
Why is it necessary to balance the chemical equation?
Explanation
In order to make law of conservation of mass, applicable on the given chemical equation, it is necessary to make number of atoms of all elements equal on L.H.S. & R.H.S. Thus balancing of equation is
required.
Q.
In order to white wash a house a man mixed 10 kg of quick lime with 30 litres of water. On
adding lime, he noticed that the water started boiling even when it was not being heated.
Explain what is the reason behind it and write the reaction involved.
Explanation
When quick lime (CaO) was added to water, formation of slaked lime [Ca(0H) 2 ]has taken place, with
the evolution of a large amount of heat. i.e. its an exothermic reaction, which caused solution to boil.
CaO(s)
+
H2O( )
Ca(OH) 2(s)
+
heat
Calcium oxide
Calcium hydroxide
Do You Know?
In a balanced chemical equation an integer precedes the formula of
each substance. This number is known as stoichiometric coefficient.
If no number is there, stoichiometric coefficient is taken as 1.
TYPES OF CHEMICAL REACTIONS
The chemical reactions are classified into various categories depending upon the types of changes
taking place. The different types of reactions are as follows :
Chemical Reactions
Combination Decomposition
Reaction
Reaction
Displacement Double
Oxidation
Reaction
Displacement and
Reaction
Reduction
Reaction
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(i)
CHEMICAL REACTIONS AND EQUATIONS
Combination Reaction. The reactions in which two or more substances combine to form a single new
substance are called combination reaction.
Combination may take place,
(i) Between two or more elements.
(ii) Between two or more compounds.
(iii) Between elements and compounds.
Some more examples of combination reactions:
(a)
Between two elements
(i)
Burning of Coal
C(s)
+
Carbon
(ii)
+
Hydrogen
+
Magnesium
+
Iron
O 2(g)
2H2O( )
Oxygen
Water
O 2(s)
2MgO(s)
Oxygen
Magnesium oxide
S(s)
FeS(s)
Sulphur
Iron sulphide
Between 2 compounds
(i)
Formation of Ammonium chloride
NH3(g)
+
Ammonia
(ii)
HCl(g)
NH4 Cl(s)
Hydrogen
Ammonium
Chloride
Chloride
Formation of Calcium Carbonate
CaO(s)
(c)
Carbon dioxide
Formation of Iron sulphide
Fe(s)
(b)
Oxygen
Burning of Magnesium in air
2Mg(s)
(iv)
CO2(g)
Formation of Water
2H2(g)
(iii)
O 2(g)
CO2(g)
CaCO3 (s)
Calcium oxide
+
Carbon
Calcium
(Quick lime)
dioxide
carbonate
Between an element and a compound
(i)
Reaction of carbon monoxide with oxygen
2CO(g)
+
O 2(g)
2CO2(g)
This is also an exothermic reactions.
Q.
How the process of respiration help us to stay alive?
Explanation
The food we eat provides us the energy to stay alive. During digestion, food is broken down into
simpler substances. For example, rice, potatoes and bread contain carbohydrates. These
carbohydrates are broken down to form glucose. This glucose combines with oxygen in the cells of our
body and provides energy. The special name of this reaction is respiration.
C6 H12O6(aq)
Glucose
+
6O2 (aq)
6O 2(aq)
Oxygen
Carbon dioxide
+
6H2O( )
+
energy
Water
So, we can say that respiration is an exothermic reaction.
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ACTIVITY - 1
Aim : To show the combination reaction between calcium oxide and water is an exothermic
process.
Materials Required: Quicklime (calcium oxide), water, beaker.
Procedure :
1.
Take 5 g of calcium oxide in a beaker.
2.
Add water to it slowly.
3.
Touch the beaker.
4.
Note down the observations.
Observation : Calcium oxide reacts with water vigorously
to form calcium hydroxide with the evolution of heat.
Chemical Reaction :
CaO (s) + H2 O (l)
Ca(OH)2 (aq) + Heat
Conclusion : The reaction between CaO (Calcium oxide) and
H2 O is a combination reaction. It is an exothermic process because heat is evolved.
ACTIVITY - 2
Aim: To show burning of magnesium ribbon in air is a combination reaction.
Materials Required: Magnesium wire, tongs, burner.
Procedure :
1.
Take a strip of magnesium ribbon and hold it with the
help of tongs.
2.
Introduce it in the flame of the burner.
Observation : Magnesium ribbon bums with dazzling light
and white substance is formed which is magnesium oxide.
This happens due to following chemical reaction.
Chemical Reaction :
2 Mg (s) + O2 (g)
2 MgO (s)
Conclusion : Burning of magnesium in presence of oxygen to form magnesium oxide is a
combination reaction.
(ii)
Decomposition Reaction. A reaction in which a single compound breaks down to produce two or
more simpler substances. i.e., a compound decomposes into simpler substances.
It is opposite to combination reactions.
There are three ways in which decomposition reactions can be carried out, i.e., energy required in
decomposition reaction can be supplied in the following ways:
(i) Heat
(ii) Electricity
(iii) Light
(1) Electrolysis. When decomposition reaction is carried out with the help of electric current, the
process is called electrolysis (‘electro’ means electric, ‘lysis’ means break down), e.g., when electric
current is passed through acidified water (water mixed with a few drops of acid so as to make it a
good conductor), it decomposes into Hydrogen and Oxygen gases.
2 H2 O (l)
electric current
2 H2 (g) + O2 (g)
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CHEMICAL REACTIONS AND EQUATIONS
ACTIVITY - 3
Aim : To demonstrate electrolysis of water.
Materials Required : Plastic mug, drilling machine or screw driver, carbon electrodes, 6 volt
battery, dil. H2 SO4 , water
Procedure :
1.
Take a plastic mug.
2.
3.
4.
Drill two holes at the base and insert carbon electrodes as shown in figure.
Fill the mug with water to its half and add a few drops of dilute sulphuric acid.
Fill a graduated measuring cylinder with water and invert it in the apparatus so that one of
the two electrodes is enclosed within it.
5.
6.
Fill another graduated cylinder with water and invert it over the second electrode.
Allow the current to pass through the voltameter and leave the apparatus undisturbed for
some time.
7. The bubble formation starts at both the electrodes.
8. Observe the volume of gases collected in the inverted measuring cylinders.
9. Collect the gases in respective cylinders and test them separately.
10. Bring a match stick near each of the gases in the cylinders and note down the observation
and write conclusion about the gas.
Plastic Mug
Hydrogen
Oxygen
Test tube
Water
Water
Graphfite rod
Anode
Switch
Rubber stopper
Cathode
6V
Battery
Electrolysis of Water
Observation : The volume of one of the gases is twice the volume of other gas. One of the
gases catches fire and burns with ‘pop’ sound whereas in other gas match stick burns brightly.
Conclusion : Water, on electrolysis decomposes to hydrogen gas and oxygen gas. Hydrogen gas
burns explosively whereas oxygen gas helps in burning, i.e., hydrogen is highly combustible and
oxygen is supporter of combustion.
(2) Thermal Decomposition. When decomposition reaction is carried out by heating, it is called
thermal decomposition reaction, e.g.,
CaCO3 (s)
[Limestone]
FeSO 4 (S)
heat
CaO (s) + CO2 (g)
[Quick lime]
heat
Fe2O3 + SO2(g) + SO3(g)
[Ferric oxide]
2Pb(NO3)2(S)
Zn CO 3 (s)
heat
heat
2PbO + 4NO2(g) + O2(g)
ZnO (s) + CO2 (g)
The process of heating ZnCO3 (Calamine), an ore of zinc in absence of air to form Zinc oxide (ZnO) and
CO (g) is also called calcination.
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ACTIVITY - 4
Aim : To show heating of lead nitrate is decomposition reaction.
Materials Required : A test tube, lead nitrate solid.
Procedure :
1. Take lead nitrate (white powder) in a test tube and hold
it in tongs.
2. Heat it over flame of burner slowly as shown in diagram.
Observation : Pungent smelling brown fumes are evolved and
brownish residue is left.
Chemical Reaction :
2 Pb(NO3 )2
heat
2PbO (s) + 4 NO2 (g) + O2 (g)
Explanation : Lead nitrate on heating decomposes to lead monoxide (brown), brown gas nitrogen
dioxide (NO2 ) and oxygen gas are evolved.
Conclusion : It is an example of decomposition reaction.
ACTIVITY - 5
Aim : To show decomposition reaction of ferrous sulphate.
Materials Required : Ferrous sulphate crystals, dry test tube, burner.
Procedure :
1. Take 2 g of ferrous sulphate crystals in a dry test tube.
2. Observe the colour of ferrous sulphate crystals.
3. Heat the crystals of ferrous sulphate over the flameof a
burner for some time.
4. Observe the crystals after heating for 5 minutes.
Observation : The green colour of ferrous sulphate crystals
changes to brownish black ferric oxide and smell of burning sulphur is observed.
Chemical Reaction :
2 FeSO4 (s)
heat
Fe2 O3 (s) + SO2 (g) + SO3 (g)
Explanation : Ferrous sulphate decomposes to form ferric oxide along with evolution of SO2 and
SO3 gases.
Conclusion : Heating of ferrous sulphate is a thermal decomposition reaction because ferrous
sulphate breaks down into simpler compounds Fe2 O3 , SO2 and SO 3.
Do You Know?
The decomposition of vegetable matter into compost
is also an example of an exothermic reaction.
(3)
Photochemical Decomposition :
Chemical reaction in which a compound decomposes into simpler substances on the absorption of
light energy is called photo-decomposition reaction.
2Agcl(s)
sunlight
Silver Chloride
(White)
2AgBr(s)
sunlight
2Ag(s) + Cl2 (g)
Silver
(Grey in colour)
2Ag(s) + Br2 (g)
Silver Bromide
Silver
Bromine
The Decomposition of a Compound with light is called “Photolysis.”
All Decomposition reaction requires energy i.e. these reactions are “Endothermic reactions.”
These reactions are used in extractions of metals.
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CHEMICAL REACTIONS AND EQUATIONS
ACTIVITY - 6
Aim : To show photochemical decomposition of silver chloride.
Materials Required : AgNO3 (aq), NaCl (aq), test tubes.
Procedure :
1.
Take 5 ml of silver nitrate solution in a test tube.
2.
Prepare sodium chloride solution in another test tube.
3.
Add sodium chloride solution into test tube containing
silver nitrate solution.
4.
Observe the colour of silver chloride formed. Dry it with the
help of filter papers and place it on the watch glass.
5.
Place the watch glass under sunlight for some time.
6.
Observe the colour of the silver chloride after some time.
Observation : White silver chloride turns grey in sunlight because silver metal is formed.
Chemical Reaction :
sunlight
2 AgCl (s)
2 Ag(s) + Cl2 (g)
Explanation : Silver chloride is photo-sensitive. It decomposes in presence of sunlight to form
silver metal and chlorine gas.
Conclusion : Decomposition of silver chloride in presence of sunlight is photochemical decomposition
reaction.
Other examples of photochemical reactions : Silver bromide and silver iodide also decompose
in the same manner.
sunlight
2 AgBr (s)
sunlight
2 AgI (s)
2 Ag(s) + Br2 (g)
2 Ag (s) + I2 (g)
These reactions are photochemical reactions which are used in black and white photography. Another
important example of decomposition reaction in our body is digestion of food. When we eat rice, wheat
or potatoes, the starch gets decomposed to simple sugar and proteins get converted into simple
substances called amino acids in our body.
(C6H10O5 )n
+
H2O
C12H22 O11
+
H2O
Proteins
Diastase
Maltase
Pep sin
C12 H22 O11
2C6H12 O6
Amino acids
We have observed all the decomposition reactions require energy either in form of heat, light or
electricity for breaking down of reactants. Therefore, they are endothermic reactions.
Endothermic Reactions: Those reactions in which heat is absorbed are called endothermic reactions.
Do You Know?
Decomposition reaction is just opposite
of the combination reaction.
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Memory Tip
Thermal
decomposition
reaction
Absorption
of heat
Decomposition
Reactions
Electro
decomposition
reaction
(iii)
Photo
decomposition
reaction
Displacement Reactions. Those reactions in which a more reactive element displaces a less reactive
element from a compound are called displacement reactions.
Potassium
K
Sodium
Na
Most Reactive
Barium
Ba
Calcium
Ca
Magnesium
Mg
Aluminium
Al
Zinc
Zn
Iron
Fe
Nickel
Ni
Tin
Sn
Lead
Pb
Hydrogen
H
Copper
Cu
Mercury
Hg
Silver
Ag
Gold
Au
Least Reactive
These reactions mostly occur in solution form, e.g.,
Zn (s) + CuSO4 (aq)
ZnSO4 (aq) + Cu (s)
Colourless
Pb + CuSO4 (aq)
PbSO4
Reddish brown
+ Cu (s)
It is a displacement reaction. Other examples are :
Mg + CuSO4
MgSO4 (aq) + Zn (s)
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CHEMICAL REACTIONS AND EQUATIONS
It shows magnesium is more reactive than Cu because it can displace Copper from Copper sulphate
solution.
Mg(s) + ZnSO4 (aq)
MgSO4 (aq) + Zn (s)
Mg (s) + FeSO4 (aq)
MgSO4 (aq) + Fe (s)
These reactions show that Mg is more reactive than Zn and Fe.
Zn (s) + FeSO4 (aq)
ZnSO4 (aq) + Fe (s)]
It shows Zn is more reactive than Fe.
On the basis of the above reactions, we can conclude Mg > Zn >Fe > Pb > Cu > Ag is the order of
reactivity.
Zn (s) + H2 SO4 (dil.)
ZnSO 4 (aq) + H2 (g)
Mg (s) + H2 SO4 (dil.)
MgSO4 (aq) + H2 (g)
These reactions show that Zn and Mg are more reactive than Hydrogen because they displace Hydrogen
from dilute acids. These are also examples of displacement reactions.
ACTIVITY - 7
Aim: To show iron is more reactive than copper.
Materials Required : Iron nails, copper sulphate
solution, test tubes.
Procedure :
1.
Take blue coloured copper sulphate solution
in a test tube.
2.
Put iron nails in it.
Observation : Colour of solution slowly changes to
light green and brown coloured copper metal gets
deposited over iron nails.
Chemical Reaction :
Fe (s) + CuSO4 (aq)
Blue
heat
FeSO4 (aq) + Cu (s)
Light green
Conclusion : Iron is more reactive than copper because iron can displace copper from copper
sulphate solution. It is an example of displacement reaction.
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Page # 53
ACTIVITY - 8
\
Aim : To show the displacement reaction between zinc granules
and dilute hydrochloric ac id or dilute sulphuric acid.
Materials Required : Zinc granules, conical flask,
dil. HCl or dil. H2SO 4.
Procedure :
1.
Take 5-6 zinc granules in a conical flask.
2.
Set the apparatus as shown in figure.
3.
Add dil. HCl or dil. H2SO 4 over it.
4.
Observe the reaction.
5.
Touch the conical flask and observe the change in
temperature.
Observation: The bubbles of hydrogen gas are observed.
The conical flask becomes hot showing that the process is exothermic.
Chemical Reaction :
Zn (s) + 2 HCl (dil)
ZnCl2 (aq) + H2 (g)
Zn (s) + H2 SO4 (dil)
ZnSO4 (aq) + H2 (g)
Conclusion : The reaction between Zn and dil. HCl or dil. H2 SO4 is a displacement reaction.
It is exothermic process. It shows zinc is more reactive than hydrogen, therefore it can displace
hydrogen from dilute acids like HCl and H2 SO4.
(iv)
Double Decomposition Reactions (Double Displacement Reactions). Those reactions in which
two different atoms or groups of atoms are displaced by other atoms or groups of atoms, i.e., two
compounds exchange their ions and one of the products formed is insoluble, e.g.,
BaCl2 (aq) + Na2SO 4 (aq)
Here, S O 24
BaSO 4 (s) + 2NaCl (aq)
ions are displacing Cl ions and Cl ions are displacing S O24 ions. Since it involves
displacement of two species, therefore, is called double displacement reactions.
If one of the products formed in the reaction is insoluble, it is also called double decomposition
reaction.
These reactions usually occur in between ionic compounds when they are dissolved in water i.e., in
aqueous solution.
These reactions are fast reactions and take place within fraction of a second.
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CHEMICAL REACTIONS AND EQUATIONS
Other examples of double displacement reactions are
AgNO3 (aq)
+
NaBr (aq)
AgBr
+ NaNO3 (aq)
AgNO3 (aq)
+
KI (aq)
AgI
+ KNO3 (aq)
FeSO 4 (aq)
+
2 NaOH (aq)
Fe (OH)2
+ Na2SO 4 (aq)
Cr2(SO4 )3
+
6 NaOH
2 Cr(OH)3
+ 3 Na2 SO4 (aq)
FeCl 3
+
3 NaOH
Fe(OH)3
+ 3 NaCl (aq)
AlCl3
+
3 NaOH
Al(OH)3
+ 3 NaCl (aq)
CuSO4
+
H2 S(g)
CuS
+ H2SO4 (aq)
MnSO4
+
H2 S (g)
MnS
+ H2SO4 (aq.)
NiCl2
+
H2 S (g)
NiS
+ 2 HCl (aq)
Pb (NO 3 )2
+
2 HCl (aq)
PbCl2 (s)
+ 2 HNO3 (aq)
CaCO3
+
2 NaCl (aq)
CaCl2 (aq)
+ Na2CO3 (aq)
Ca(NO3 )2
+
(NH4 )2 CO3
CaCO3
+ 2 NH4NO3
ZnSO4
+
H2S
ZnS
+ H2SO4 (aq)
ACTIVITY - 9
Aim : To show reaction between sodium sulphate solution and barium chloride solution is double
displacement reaction (precipitation reaction).
Materials Required : Barium chloride solution, sodium sulphate solution, two test tubes.
Procedure :
1.
Take sodium sulphate solution in a test tube.
2.
Add few drops of solution of barium chloride.
Observation : White precipitate is formed.
Chemical Reaction :
Na2 SO4 (aq) + BaCl2 (aq)
BaSO4
+ 2NaCl (aq)
Conclusion : Reaction between sodium sulphate solution and barium chloride solution is
double displacement reaction.
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ACTIVITY - 10
Aim : To show the reaction between lead nitrate and potassium iodide is double decomposition
reaction (precipitation reaction).
Materials Required : Test tubes, lead nitrate solution, potassium iodide solution.
Procedure :
1.
Take lead nitrate solution in a test tube.
2.
Add potassium iodide solution to it.
3.
Observe the changes taking place in the solution.
Observation : Yellow precipitate is formed.
Chemical Reaction and Explanation : Lead nitrate reacts with potassium iodide to form lead
iodide which is insoluble in water and yellow in colour. It is called precipitate. The reaction is also
called precipitation reaction.
Pb(NO 3)2 (aq) + 2KI (aq)
PbI2 (s) + 2 KNO3 (aq)
Conclusion : The reaction between lead nitrate and potassium iodide is double decomposition
reaction. Since Pb is insoluble called precipitate, therefore, this reaction is also called precipitation
reaction.
(v)
Neutralization Reactions. Those reactions in which acid or acidic oxide reacts with base or basic
oxide to form salt and water are called neutralization reactions, e.g.,
NaOH
+
HNO3
NaNO3
+ H2O
2 NaOH
+
H2 SO4
Na2SO4
+ 2 H2 O
KOH
+
HCl
KCl
+ H2O
KOH
+
HNO3
KNO3
+ H2O
2KOH
+
H2 SO4
K2SO4
+ 2H2O
CH3COOH
+
NaOH
CH3COONa
+ H2O
+
2NaOH
+ 2H2O
When salt of weak acid reacts with strong acid, it is also called neutralization reaction.
Na2CO3
+
2HCl
2NaCl
+ H2 O + CO2
CH3COONa
+
HCl
CH3COOH
+ NaCl
When acidic salt reacts with base to form salt and water, it is also called neutralization reaction.
NaHCO3
+
NaOH
Na2CO3
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(vi)
CHEMICAL REACTIONS AND EQUATIONS
Oxidation and Reduction
(1) Oxidation.
(a) It is a process in which Oxygen or an electronegative element is added.
(b) It can also be defined as a process in which Hydrogen or an electropositive element is removed.
(c) In terms of electronic concept, oxidation is a process in which loss of electrons takes place.
4Na + O2
2 Na2 O
(Addition of oxygen)
2Mg + O2
2 MgO
(Addition of oxygen)
Fe
Fe
(Loss of electron)
2+
3+
+e
2 Fe + 3 Cl2
2 FeCl3
(Addition of electronegative element)
Hg2Cl2
Hg + HgCl2
(Removal of electropositive element)
Cu
300o C
CH3CH2OH
CH3CHO + H2 (Removal of Hydrogn)
(2) Reduction.
(a) It is a process in which addition of Hydrogen or an electropositive element takes place.
(b) It is also defined as a process in which Oxygen or an electronegative element is removed.
(c) In electronic concept, reduction process involves gain of electrons.
2 Na
+
H2
2NaH
(Addition of Hydrogen)
CuO
+
H2
Cu + H2O
(Removal of Oxygen and addition of hydrogen)
Fe3+
+
e
Fe 2+
(Gain of electron)
Hg
+
HgCl2
Hg2 Cl2
(Addition of an electropositive element)
Cu
+
CuCl2
Cu 2Cl2
(Addition of an electropositive element)
Cl2
(Removal of an electronegative element)
AuCl3
AuCl
+
ACTIVITY - 11
Aim: To study oxidation of copper to copper (II) oxide.
Method: Heat a china dish containing about 1 9 copper powder .
Now answer: What do you observe?
Discussion: It is observed that the brown copper powder gets coated with black copper (II)
oxide.
Wire gauze
Tripod stand
Burner
Oxidation of copper to copper oxide
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Conclusion:
Copper (brown in colour) on heating combines with oxygen to form black copper (II) oxide.
2Cu(s)
+
Copper(Brown)
O2 (g)
2CuO(s)
Oxygen
Copper (II) oxide (Black)
Here, we can say that copper is being oxidised, as it is gaining oxygen. In the above activity if
hydrogen gas is passed over product (CuO) and the black coating on the surface becomes
brown because reverse reaction takes place.
CuO(s)
+
Heat
H2(g)
Cu(s) +
H2 O( )
Here, we can say that copper oxide is being reducing, as it is loosing oxygen and hydrogen is
being oxidised.
Redox Reactions : Those reactions in which oxidation and reduction take place simultaneously are
called redox reactions, e.g.,
(i)
(ii)
Mn4+ + 2e
Mn 2+
(Reduction) [Gain of electrons]
2 Cl
Cl2 + 2e
(Oxidation) [Loss of electron]
Cu (s) + I2 (s)
CuI2 (s)
Cu (s)
Cu2+ (aq) + 2e
(Oxidation) [Loss of electron]
I2 (s) + 2e
2I
(Reduction) [Gain of electron]
Cu (s) + I2 (s)
CuI2 + 2e
Cu (s) + I2 (s)
CuI2 (s)
is a Redox reaction.
Oxidising Agent. It is a substance which can
(i) add oxygen or an electronegative element to other materials.
(ii) remove hydrogen or an electropositive element from other materials.
(iii) gain electrons.
Oxidising agent itself gets reduced.
Reducing Agent. It is a substance which can
(i) add hydrogen or an electropositive element to other materials.
(ii) remove oxygen or an electronegative element from other materials
(iii) lose electrons.
Reducing agent itself gets oxidised.
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Example 1.
CHEMICAL REACTIONS AND EQUATIONS
Fe + S
FeS
Fe
Fe2+ + 2e
(Oxidation)
S + 2e
S2
(Reduction)
Fe is losing electrons, therefore, it acts as a Reducing agent.
S is gaining electrons, therefore, it acts as an Oxidising agent.
Fe is getting oxidised to Fe2+ (Ferrous ion) whereas S gets reduced to S2 (Sulphide ion)
Example 2.
Cu (s) + 2AgNO3 (aq)
Cu (NO 3)2 (aq) + 2 Ag (s)
Cu (s)
Cu2+
2 Ag+ + 2e
2 Ag
Cu (s) + 2 Ag+ (aq)
Cu2+ (aq) + 2 Ag (s)
+ 2e
(Oxidation)
(Reduction)
Cu is a reducing agent because it is losing electrons whereas Ag + is an oxidising agent.
Example 3.
Fe 2O3 is an oxidizing agent whereas Al is a readucing agent.
Example 4.
Zn + CuSO4
ZnSO4 + Cu
Zn is a reducing agent whereas Cu 2+ is an oxidizing agent
Example 5.
2 Na + Cl2
2NaCl
2 Na
2 Na+ + 2e
Cl2 + 2e
2Cl
[Oxidation]
Na is a reducing agent whereas Cl2 is an oxidizing agent.
Example 6.
H2 S is a reducing agent whereas SO2 is an oxidizing agent.
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Page # 59
Memory Tip
Reduction
reaction
Oxidation
reaction
Combination
reaction
Chemical
Reaction
Double displacement
reaction
Decomposition
reaction
Displacement
reaction
EFFECTS OF OXIDATION IN EVERYDAY LIFE
Oxidation has damaging effect on metals as well as on food. The damaging effect of oxidation on
metals is studied as corrosion and that on food is studied as rancidity.
Thus there are two common effects of oxidation reactions are as
(I)
(I)
Corrosion of metals
(II) Rancidity of food
Corrosion of metals :– Corrosion is the process of deterioration of metals as a result of its reaction
with air, moisture and acids. (Present in environment) surrounding it.
The corrosion causes damage to buildings, bridges, ships and many other articles especially made of iron.
Rust : Iron corrode readily when exposed to moisture and gets covered with a brown flaky substance
called rust. It is called rusting of iron, Rust is a hydrated Iron (III) oxide. [Fe2O3 · 2H2O]
Oil
Iron nail
Iron nail
Iron nail
Tap water
Rust
Dry water
Anhydrous
calcium chloride (a)
(b)
Boiled
water
(c)
Rusting of iron takes place under the following conditions –
(a) Presence of air (or oxygen)
(b) Presence of water (or moisture) It has been observed that
(c) Presence of impurities in the metal speed up the rusting process. Pure iron does not rust.
(d) Presence of electrolytes in water also speeds up the process of rusting
(e) The position of the metal in the electrochemical series determines the extent of corrosion. More
the reactivity of the metal, there will be more possibility of the metal getting corroded.
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CHEMICAL REACTIONS AND EQUATIONS
Other examples of corrosion are –
(i) Copper reacts with moist carbon dioxide in the air and slowly loses its shiny brown
surface and acquires a green coating of basic copper carbonate.
(ii) Silver articles become black after sometime when exposed to air because it reacts with
sulphur to form a coating of silver sulphide.
(iii) Lead or stainless steel lose their lusture due to corrosion.
(iv) Unreactive metals such as Gold, Platinum, Palladium, Titanium etc. do not corrode.
Prevention of Rusting.
(II)
1.
The iron articles should be painted.
2.
The machine parts should be oiled and greased.
3.
Galvanised iron pipes are used for water supply.
4.
Iron can be coated with chromium to prevent rusting.
Rancidity. The oxidation of oils or fats in food, resulting into a bad taste and bad smell is called
rancidity. It is caused due to prolonged exposure of food in air. Oxygen present in air oxidise fats/oil
present in food and form volatile substances, which have bad odour.
Do You Know?
Vitamin E and Vitamin C (Ascorbic acid) are
the two antioxidants occuring in natural fats.
Prevention of rancidity :–
(i) Rancidity can be prevented by adding antioxidants to foods containing fats and oils. Antioxidants
are reducing agents so when they are added to food it do not get oxidised easily and hence do not
turn rancid. The two common anti oxidants are –
(a) BHA (Butylated Hydroxy Anisole)
(b) BHT (Butylated Hydroxy Toluene)
(ii) Rancidity can be prevented by packaging fat and oil containing foods in nitrogen gas.
(iii) It can be retarted by keeping food in refrigerator.
(iv) It can also be retarded by storing food in air tight containers.
(v) It can be retarded by storing foods away from light.
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CHEMICAL REACTIONS AND EQUATIONS
Page # 61
SOLVED PROBLEMS
Ex.1
Translate the following statements into chemical equations and then balance them.
(A) Hydrogen gas combines with nitrogen to form ammonia
(B) Hydrogen sulphide gas burns in air to give water and sulphur dioxide.
(C) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium
sulphate.
(D) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.
Sol.
(A) N2(g) + 3H2(g)
(B) 2H2S + 3O 2
2NH3(g)
2H2O + 2SO2
from air
(C) 3BaCl2(aq) + Al2(SO 4)3(aq)
2AlCl3(aq) + 3BaSO4(s)
White ppt.
(D) 2K(s) + 2H2O(l)
Ex.2
2KOH + H2(g)
Balance the following chemical equations.
(A) HNO3 + Ca(OH)2
(B) NaOH + H2SO4
Sol.
Ca(NO3)2 + H2O
Na2SO4 + H2O
(A) 2HNO3 + Ca(OH)2
(B) 2NaOH + H2SO 4
Ex.3
Ca(NO3)2 + 2H2O
Na2SO4 + 2H2O
Write the balanced chemical equations for the following reactions.
(A) Calcium hydroxide + Carbon dioxide
(B) Zinc + Silver nitrate
Calcium carbonate + water
Zinc nitrate + Silver
(C) Aluminium + copper chloride
Aluminium chloride + Copper
(D) Barium chloride + Potassium sulphate
Sol.
(A) Ca(OH)2
+
calcium
CO2
carbon
hydroxide dioxide
(B)
Zn +
2AgNO3
zinc silver nitrate
(C)
2Al
+
aluminium
3CuCl2
copper
chloride
(B)
BaCl2 +
Barium sulphate + Potassium chloride.
CaCO3 + H2O
calcium
carbonate
Zn(NO3)2
+
2Ag
zinc nitrate
silver
2AlCl3
+
aluminium
3Cu
copper
chloride
K2SO 4
BaSO4
+
2KCl
barium
potassium
barium
potassium
chloride
sulphate
sulphate
chloride
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Page # 62
Ex.4
CHEMICAL REACTIONS AND EQUATIONS
Write the balanced chemical equation for the following and identify the type of reaction in each case
(A) Potassium bromide(aq) + Barium iodide(aq)
(B) Zinc carbonate (s)
Zinc oxide (s) + Carbon dioxide(g)
(C) Hydrogen(g) + Chlorine(g)
Hydrogen chloride(g)
(D) Magnesium(s) + Hydrochloridc acid(aq)
Sol.
Potassium iodide(aq) + Barium bromide(s)
(A) 2KBr(aq) + BaI2(aq)
Magnesium chloride(aq) + Hydrogen(g)
2KI(aq) + BaBr2(aq)
This reaction is a double-displacement reaction.
(B) ZnCO 3(s)
ZnO(s) + CO2(g)
This reaction is a decomposition reaction
(C) H2(g) + Cl 2(g)
2HCl(g) [Combination Reaction]
(D) Mg(s) + 2HCl(aq.)
MgCl2(aq.) + H2(g) [Displacement Reaction]
Ex.5
Why should a magnesium ribbon be cleaned before burning in air?
Sol.
Magnesium reacts with the constituent gases of the atmosphere to form various compounds which get
deposited over its surface. The ribbon is cleaned before burning to remove the layer of these compounds
so that pure magnesium can burn in air.
Ex.6
In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by
copper metal. Write down the reaction involved.
Sol.
2AgNO 3(aq) + Cu(s)
2Ag(s)
+
Cu(NO3)2(aq)
(silver nitrate) (copper) (silver metal) (copper(II) nitrate)
Ex.7
A shiny brown coloured element 'X' on heating in air becomes black in colour. Name the element 'X' and
the black coloured compound formed.
Sol.
An element on heating in air changes in its oxide. The brownish element which forms black oxide is
copper. So,
Name of the element
Copper (Cu)
Name of black compound:
Copper(II) oxide, (CuO)
Reaction
+
2Cu(s)
O2(g)
copper (brown) from air
Heat
2CuO(s)
copper(II) oxide (black)
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CHEMICAL REACTIONS AND EQUATIONS
Page # 63
Ex.8
What happens chemically when quick lime is added or water ?
Sol.
Calcium hydroxide (or slaked lime) is formed accompanied by a hissing sound. So much heat is evolved
during the reaction that the reaction mixture starts boiling. The chemical equation for the reaction
is :
CaO(s) + H 2O(aq)
Ca(OH)2(s) + heat
(Quick lime)
Ex.9
(Slaked lime)
What is an oxidation reaction ? Identify in the following reactions :
(i) the substance oxidised
ZnO + C
Sol.
(ii) the substance reduced.
Zn + CO
Oxidation involves the addition of oxygen or the removal of hydrogen in a chemical reaction while
reduction involves the addition of hydrogen or removal of organ.
In the given reaction :
(i) Carbon (C) is oxidised to carbon monoxide (CO).
(ii) Zinc oxide (ZnO) is reduced to zinc (Zn)
Ex.10 Which gas is evolved when dilute hydrochloric acid reacts with zinc ? Write the molecular formula
of the gas.
Sol.
Hydrogen gas is evolved. Its molecular formula is H 2.
Ex.11 State any two observation in an activity which may suggest that a chemical reaction has taken
place. Give examples in support of your answer.
Sol.
(i) In a tube take small amount of solid sodium carbonate (Na 2CO3). To this add a few drops of
hydrocloric acid.
(ii) A colourless and odourless gas will evolve which shows that a chemical reaction has taken place.
The gas will turn lime water milky when passed through it.
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CHEMICAL REACTIONS AND EQUATIONS
Ex.12 Identify the type of reaction in the following examples :
(i) Na 2SO4(aq) + BaCl2(aq)
(ii) Fe(s) + CuSO 4(aq)
(iii) 2H2(g) + O2(g)
Sol.
BaSO 4(s) + 2NaCl(aq)
FeSO4(aq) + Cu(s)
2H 2O( )
(i) It is an example of double displacement reaction.
(ii) It is an example of displacement reaction.
(iii) It is an example of combination reaction.
Ex.13 Solid calcium oxide was taken in a container and water was added slowly to it
(i)
State two observations made in the experiment.
(ii) Write the name of the chemical formula of the product.
Sol.
(i)
Water will start boiling and hissing noise will be produced.
(ii) Calcium hydroxide (slaked lime) will be formed.
CaO(s) + H 2O(aq)
Ca(OH)2(s) + heat
Calcium oxide
Calcium hydroxide
Ex.14 A house wife wanted her house to be white washed. She bought 10 kg of quick lime from the
market and dissolved in 30 litres of water. On adding lime to water, she noticed that the water
started boiling even when it was not being heated. Give reason for her observation. Write the
corresponding equation and name the product formed.
Sol.
A supension of slaked lime also called calcium hydroxide is formed when water is added to quick
lime.
CaO(s) + H 2O( )
Ca(OH)2(s) + heat
(Slaked lime)
Since the reaction is highly exothermic, the solution started although it was not being heated.
The suspension of slaked lime is allowed to cool for sometime, preferably overnight. It is then decanted
and the liquid obtained is used for white washing.
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CHEMICAL REACTIONS AND EQUATIONS
Page # 65
NCERT QUESTIONS WITH SOLUTIONS
Q.1
Why should a magnesium ribbon be cleaned before it is burnt in air?
Ans.
Magnesium is an extremely reactive metal. When stored, it reacts with oxygen to form a layer of
magnesium oxide on its surface. This layer of magnesium oxide is quite stable and prevents further
reaction of magnesium with oxygen. The magnesium ribbon is cleaned by sand paper for removing this
layer so that the underlying metal can be exposed to air.
Q.2
Write the balanced equation for the following chemical reactios.
(i) Hydrogen + Chlorine
Hydrogen chloride
(ii) Berium chloride + Aluminium sulphate
(iii) Sodium + Water
Ans.
(i) H2 (g) + Cl2(g)
2HCl(g)
(ii) 3BaCl2(aq) + Al2 (SO4 )3(aq)
(iii) 2Na(s) + 2H2O( )
Q.3
Barium sulphate + Aluminium chloride
Sodium hydroxide + Hydrogen
3BaSO 3(s) + 2AlCl3 (aq)
2NaOH(aq) + H2 (g)
Write a balanced chemical equation with state symbols for the following reactions.
(i) Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate
and the solution of sodium chloride.
(ii) Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) reacts with
hydrochloric acid solution (in water) to produce sodium chloride solution and water.
Ans.
(i) BaCl2(aq) + Na2 SO4 (aq)
(ii) NaOH(aq) + HCl(aq)
Q.4
BaSO 4(s) + 2NaCl(aq)
NaCl(aq) + H2 O( )
A solution of a substance 'X' is used for white washing.
(i) Name the substance 'X' and write its formula.
Ans.
(ii) Write the reaction of the substance 'X' with water.
(i) The substance 'X' is calcium oxide. Its chemical foluma is CaO.
(ii) Calcium oxide reacts vigorously with water to form calcium hydroxide (slaked lime).
CaO(s)
+
Calcium oxide
(Quick lime)
H2O( )
Ca(OH)2 (aq)
Water
Calcium hydroxide
(Slaked lime)
Q.5
Why is the amount of gas collected in one of the test tubes is double of the amount collected in the
other? Name this gas.
Ans.
Water (H2 O) contains two parts hydrogen and one part oxygen. Therefore, the amount of hydrogen
and oxygen produced during electrolysis of water is in a 2 : 1 ratio. During electrolysis, since hydrogen
goes to one test tube and oxygen goes to another, the amount of gas collected in one of the test
tubes is double of the amount collected in the other.
Q.6
Why does the colour of copper sulphate solution change when an iron nail is dipped in it?
Ans.
When an iron nail is placed in a copper sulphate solution, iron displaces copper from copper sulphate
solution forming iron sulphate, which is green in colour.
Fe(s) +
Iron
CuSO4 (aq)
Copper sulphate
FeSO 4(aq)
+
Iron sulphate
(Blue colour)
(Green colour)
Cu(s)
Copper
Therefore, the blue colour of copper sulphate solution fades and green colour appears.
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CHEMICAL REACTIONS AND EQUATIONS
Q.7
Give an example of a double displacement reaction other than the one given in Activity 1.10.
Ans.
Sodium carbonate reacts with calcium chloride to form calcium carbonate and sodium chloride.
Na2 CO3(aq)
+
CaCl2(aq)
CaCO3 (s)
+
2NaCl(aq)
Sodium
Calcium
Calcium
Sodium
carbonate
chloride
carbonate
chloride
In this reaction, sodium carbonate and calcium chloride exchange ions to form two new compounds.
Hence, it is a double displacement reaction.
Q.8
Ans.
Identify the substances that are oxidised and the substances that are reduced in the followiing
reactions.
(i) 4Na(s)
+
O2(g)
2Na2 O(s)
+
O2 (g)
(ii) CuO(s)
+
H2(g)
Cu(s)
+
H2O( )
(i) Sodium (Na) is oxidised as it gains oxygen and oxygen gets reduced.
(ii) Copper oxide (CuO) is reduced to copper (Cu) while hydrogen (H2 ) gets oxidised to water (H2 O).
Q.9
Which of the statements about the reaction below are incorrect?
2PbO(s)
+
C(s)
2Pb(s) +
CO2(g)
(a) Lead is getting reduced.
(b) Carbon dioxide is getting oxidised.
(c) Carbon is getting oxidised.
(d) Lead oxide is getting reduced.
(1) (a) and (b)
Ans.
(1) (a) and (b)
Q.10
Fe 2O 3
+
(2) (a) and (c)
(3) (a), (b) and (c)
2Al
+
Al2O3
(4) all
2Fe
The above reaction is an example of a
(1) Combination reaction.
(2) Double displacement reaction.
(3) Decomposition reaction.
(4) Displacement reaction.
Ans.
(4) The given reaction is an example of a displacement reaction.
Q.11
What happens when dilute hydrochloric add is added to iron filings? Tick the correct answer.
(1) Hydrogen gas and iron chloride are produced.
(2) Chlorine gas and iron hydroxide are produced.
(3) No reaction takes place.
(4) Iron salt and water are produced.
Ans.
(1) Hydrogen gas and iron chloride are produced. The reaction is as follows:
Fe(s)
+
2HCl(aq)
FeCl2 (aq)
+
H2
Q.12
What is a balanced chemical equation? Why should chemical equations be balanced ?
Ans.
A reaction which has an equal number of atoms of all the elements on both sides of the chemical
equation is called a balanced chemical equation. The law of conservation of mass states that mass can
neither be created nor destroyed. Hence, in a chemical reaction, the total mass of reactants should,
be equal to the total mass of the products. It means that the total number of atoms of each element
should be equal on both sides of a chemical equation. Hence, it is for this reason that chemical
equations should be balanced.
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Q.13
Page # 67
Translate the following statements into chemical equations and then balance them.
(a) Hydrogen gas combines with nitrogen to form ammonia.
(b) Hydrogen sulphide gas burns in air to give water and sulphur dioxide.
(c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of
barium sulphate.
(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.
Ans.
(a) 3H2 (g) + N2 (g)
2NH3(g)
(b) 2H2 S(g) + 3O2 (g)
2H2 O( ) + 2SO2 (g)
(c) 3BaCl2(aq) +Al2 (SO4 )3 (aq)
(d) 2K(s) + 2H2O( )
Q.14
2KOH(aq) + H2 (g)
Balance the following chemical equations.
(a) HNO3 + Ca(OH)2
Ca(NO3 )2 + H2 O
(b) NaOH + H2SO 4
Ans.
Na2 SO4 + H2 O
(c) NaCl + AgNO3
AgCl + NaNO3
(d) BaCl2 + H2SO4
BaSO 4 + HCl
(a) 2HNO 3 + Ca(OH)2
Ca(NO3 )2 + H2 (g)
(b) 2NaOH + H2 SO4
Na2 SO4 + 2H2O
(c) NaCl + AgNO3
AgCl + NaNO3
(d) BaCl2+ H2 SO4
Q.15
2AlCl3 (aq) + 3BaSO4 (s)
BaSO4 + 2HCl
Write the balanced chemical equations for the following reactions.
(a) Calcium hydroxide + Carbon dioxide
(b) Zinc + Silver nitrate
Zinc nitrate + Silver
(c) Aluminium + Copper chloride
Alumiium chloride + Copper
(d) Barium chloride + Potassium sulhate
Ans.
(a) Ca(OH) 2 + CO2
Barium sulphate + Potassium chloride
CaCO 3 + H2O
(b)Zn + 2AgNO3
Zn(NO3)2 + 2Ag
(c) 2Al + 3CuCl2
2AlCl3 + 3Cu
(d) BaCl2 + K2 SO4
Q.16
Calcium carbonate + Water
BaSO4 + 2KCl
Write the balanced chemical equation for the following and identify the type of reaction in each case.
(a) Potassium iodide(aq) + Barium iodide(aq)
(b) Zinc carbonate(s)
Zinc oxide(s) + Carbon dioxide(g)
(c) Hydrogen(g) + Chlorine(g)
Hydrogen chloride(g)
(d) Magnesium(s) + Hydrochloric acid(aq)
Ans.
(a) 2KBr(aq) + BaIz (aq)
(b) ZnCO 3(s)
Carbon dioxide(g)
Magnesium chloride(aq) + Hydrogen(g)
2KI(aq) + BaBr2 (s); Double displacement reaction
ZnO(s) + CO2 (g) ; Decomposition reaction
(c) H2 (g) + Cl2(g)
(d) Mg(s) + 2HCl(aq)
2HCl(g) ; Combination reaction
MgCl2(aq) + H2(g) ; Displacement reaction
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CHEMICAL REACTIONS AND EQUATIONS
Q.17
What does one mean by exothermic and endothermic reactions? Give examples.
Ans.
Chemical'reactions that release energy in the form of heat, light, or sound are called exothermic
reaction.
Example: Mixture of sodium and chlorine to yield table salt
Na(s) +
1
Cl (g)
2 2
NaCl(s) + 411 kL of energy
In other words, combination reactions are exothermic.
Reactions that absorb energy or require energy in order to proceed are called endothermic reactions.
For example: In the process of photosynthesis, plants use the energy from the sun to convert carbon
dioxide and water to glucose and oxygen.
Sunlight
6CO 2(g) + 6H2 O( )
C6 H12O6 (aq) + 6)2 (g
Glucose
Q.18
Why is respiration considerd an exothermic reaction ? Explain.
Ans.
Energy is required to support life. Energy in our body is obtained from the food we eat. During
digestion, large molecules of food are broken down into simpler substances such as glucose. Glucose
combines with oxygen in the cells and provides energy. The special name of this combustion reaction is
respiration. Since energy is released in the whole process, it is an exothermic process.
C6 H12O6(aq)
+
Glucose
6O2(g)
6CO2 (g)
Oxygen
Carbon dioxide
+
6H2O( )
+
Energy
Water
Q.19
Why are decomposition reactions called the opposite of combination reactions? Write equations for
these reactions.
Ans.
Decomposition reactions are those in which a compound breaks down to form two or more substances.
These reactions require a source of energy to proceed. Thus, they are the exact opposite of combination reactions in which two or more substances combine to give a new substance with the release of
energy.
Decomposition reaction: AB + Energy
2H2 O( )
Elect rolysis
2H2 (g) + O2 (g)
Combination reaction: A + B
2H2 (g) + O2 (g)
A +B
AB + Energy
2H2 O( ) + Energy
Q.20
Write one equation each for decomposition reactions where energy is supplied in the form of heat, light
or electricity.
Ans.
(a)
(b)
Thermal decomposition:
2FeSO4(s)
Fe 2O3 (g)
Ferrous sulphate
Ferric oxide
SO2 (g)
+
Sulphur dioxide
SO 3(g)
Sulphur trioxide
Decomposition by light:
2AgCl(s)
Ligh t
Silver chloride
(c)
+
2Ag(s)
+
Silver
Cl2(s)
Chlorine
Decomposition by electricity:
2Al2O3 (aq)
Aluminium oxide
Electricity
4Al(s)
Aluminium
+
3O 3(g)
Oxygen
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Page # 69
Q.21
What is the difference betuJeen dispiacemen[ and double displacement reactions? Write equations for
these reactions.
Ans.
In a displacement reaction, a more reactive element replaces a less reactive element from a
compound.
A + BX
AX + B; where A is more reactive than B
In a double displacement reaction, two atoms or a group of atoms shift places to form new compounds.
AB + CD
AD + CB
For example:
Displacement reaction:
CuSO 4(aq) + Zn(s)
ZnSO 4(aq) + Cu(s)
Double displacement reaction:
Na2 SO4 (aq) + BaCl2 (aq)
BaSO4(s) + 2NaCl(aq)
Q.22
In the refining of silver, the recovery of silver from silver nitrate solutior. involved displacement by
copper metal. Write down the reaction involved.
Ans.
2AgNO 3(aq)
+
Silver nitrate
Cu(s)
Cu(NO 3)2(aq) +
2Ag(s)
Copper
Copper nitrate
Silver
Q.23
What do you mean by a precipitation reaction? Explain by giving examples.
Ans.
A reaction in which an insoluble solid (called precipitate) is formed is called a precipitation reaction.
For example:
Na2 CO3(aq)
+
Sodium carbonate
CaCl2 (aq)
CaCO3 (s)
Calcium chloride
Calcium carbonate
+
2NaCl(aq)
Sodium chloride
In this reaction, calcium carbonate is obtained as a precipitate. Hence, it is a precipitation reaction.
Another example of precipitation reaction is:
Na2 SO4(aq)
+
BaCl2(aq)
BaSO4(s)
+
2NaCl(aq)
Sodium sulphate
Barium chloride
Barium sulphate
Sodium chloride
In this reaction, barium sulphate is obtained as a precipitate.
Q.24
Explain the following in terms of gain or loss of oxygen with two examples each.
(a) Oxidation
Ans.
(b) Reduction
(a) Oxidation is the gain of oxygen.
For example:
CO 2 + H 2
(i)
CO + H2O
Addition of oxygen-oxidation
(ii)
2Cu + O2
CuO
2
Gain of oxygen - oxidation
In equation (i), H2 is oxidized to H2O and in equation (ii), Cu is oxidised to CuO.
(b) Reduction is the loss of oxygen.
For example:
CO 2 + H 2
(i)
CO + H2O
Removal of oxygen - reduction
(ii)
CuO + H2
Cu + H2O
Loss of oxygen - reduction
in equation (i), CO2 is reduced to CO and in equation (ii), CuO is reduced ro Cu.
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Q.25
CHEMICAL REACTIONS AND EQUATIONS
A shiny brown-cloured element 'X' on heating in air becomes black in colour. Name the element 'X' and
the black coloured compound formed.
Ans.
‘X’ is copper (Cu) and the black-coloured ocmpound formed is copper oxide (CuO). The equation of the
reaction involved on heating copper is given below.
2Cu
+
Heat
O2
2CuO
(Shiny brown in colour)
(Black in colour)
Q.26
Why do we apply paint on iron articles?
Ans.
Iron articles are painted because it prevents them from rusting. When painted, the contact of iron
articles from moisture and air is cut off. Hence, rusting is prevented. Their presence is essential for
rusting to take place.
Q.27
Oil and fat containing food items are flushed with nitrogen. Why?
Ans.
Nitrogen is an inert gas and does not easily read with these substances. On the other hand, oxygen
reacts with food substances and makes them rancid. Thus, bags used in packing food items are flushed
with nitrogen gas to remove oxygen inside the pack. When oxygen is not present inside the pack,
rancidity of oil and fat containing food items is avoided.
Q.28
Explain the following terms with one example each.
(a) Corrosion
Ans.
(b) Rancidity
(a) Corrosion: Corrosion is defined as a process where materials, usually metals, deteriorate as a
result of a chemical reaction with air, mOisture, chemicals, etc.
For example, iron, in the presence of moisture, reacts with oxygen to form hydrated iron oxide.
4Fe
+
3O2
+
nH2O
2Fe2O3 .nH2O
Hydrated iron oxide
This hydrated iron oxide is rust.
(b) Rancidity: The process of oxidation of fats and oils that can be easily noticed by the change in
taste and smell is known as rancidity.
For example, the taste and smell of butter changes when kept for long.
Rancidity can be avoided by:
(1) Storing fooo in air tight containers
(2) Storing fooo in refrigerators
(3) Adding antioxidants
(4) Storing food in an environment of nitrogen
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CHEMICAL REACTIONS AND EQUATIONS
EXERCISE – I
Page # 71
BOARD PROBLEMS
Type I- Very Short Answer Questions
Q.1
Why does not a wall immediately acquire a white
Q.13
lead nitrate crystals are heated in a dry test
tube?
colour when a coating of slaked lime is applied
on it?
[C.B.S.E. 2010]
Q.14
Q.2
What is ruet?
Q.3
What is the difference b/w the following 2
Q.15
[C.B.S.E. 2011]
(a) Mg + 2HCl
In the reaction MnO2 + 4HCl
MnCl2 + 2H2O
Complete the equation:-
[C.B.S.E. 2010]
Fe 2O3 + 2Al
MgCl2 + H 2
(b) NaOH + HCl
NaCl + H 2O
Q.16
Q.5
What is the role of oxidising agent in a reaction?
[C.B.S.E. 2010]
Q.6
What is meant by a skeletal chemical equation?
[C.B.S.E. 2010]
Q.7
On what basis is a chemical equation balanced?
[C.B.S.E. 2010]
Q.8
Balance following chemical equation:Heat
Take a small amount of calcium oxide or quick
lime in a beaker and slowly add water to this.
Is there any change in temperature?
Suggest 2 ways to check the rancidity of food
articles.
[C.B.S.E. 2011, 2012]
Pb(NO3)2(s)
[C.B.S.E. 2010]
+ Cl 2. Identify which one is reduced and which
one is oxidized?
[C.B.S.E. 2010]
reactions?
Q.4
What is the brown coloured gas evolved when
[C.B.S.E. 2010, 2011]
Q.17
Which chemical process is used for obtaining
a metal from its oxide?
[C.B.S.E. 2010]
Type II - Short Answer Type Questions
Q.18
Write balance chemical equation “during
respiration combustion of glucose takes place
producing carbon dioxide water and energy”.
Q.19
A zinc rod is left for nearly 20 minutes in a
copper sulphate solution. What change would
you observe in zinc rod?
Pbo(s) + NO2(g) + O2(g)
[C.B.S.E. 2009]
Q.20
Name a reducing agent that can be used to
obtain manganese from manganese dioxide.
Write balanced chemical equation for the
reaction?
[C.B.S.E. Delhi 2009]
Q.21
Give reason, silver articles become black after
sometime when exposed to air?
Q.9
Writ e a balanced chemic al e quat ion to
represent the following equation:- Iron reacts
with stream to form Iron (II, III) oxide and
Hydrogen gas.[C.B.S.E. Sample paper 2011]
Q.10
Balance the following chemical equation.
(i) FeCl2 + H 2S
HCl + Fes
(ii) HNO3 + Ca(OH)2
Ca(NO 3)2 + H 2O
[C.B.S.E. 2008]
Q.22
What is the role of catalyest in a chemical
reaction?
[C.B.S.E. 2007]
What happens chemically when Quick lime is
added to water?
[C.B.S.E. 2010]
Q.23
Name 2 salts which are used in black and white
Q.11
Q.12
[C.B.S.E. 2008]
photography?
Give one example of each exothermic reaction
and endothermic reaction? [C.B.S.E. 2010]
Q.24
[C.B.S.E. 2010, 11]
State the essential requriement for rusting?
[C.B.S.E. 2013]
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Page # 72
CHEMICAL REACTIONS AND EQUATIONS
Type III- Long Answer Type Questions
Q.25
Q.31
A brown substance “X” on heating in air forms
When a water insoluble substance “X” is added
a substance “Y”. When hydrogen gas is passed
to dil. Hydrochloric acid, a colourless, odourless
over heated “Y”. It again changes back into
gas is evolved. When the gas is passed through
“X”.
lime water, it turns milky. Write the formula
[C.B.S.E. 2010]
(i) Name the substance X and Y.
of gas evolved and balanced chemical equation
of the reaction.
(ii) Name the chemical processes occuring
during both changes.
Q.26
(a) Write one equation each for decomposition
(iii) Write chemical equations?
reaction when energy is supplied in the form
of (i) Heat (ii) Light.
(b) Account for following:-
Q.32
(i) Paint is applied on Iron articles.
Explain why:-
[C.B.S.E. 2011]
(i) Respiration is an Exothermic reaction.
(ii) Oil and fat containing food items are flushed
with nitrogen.
[C.B.S.E. 2011]
(ii) When blue salt of CuSO4 is heated it
becomes colourless?
Q.27
A green coloured hydrated salt of Iron loses
its water of crystallisation and smell of burning
sulphur is given. Identify the salt and write
chemical equation.
[C.B.S.E. 2011]
Q.33
In electrolysis of water
[C.B.S.E. 2012]
(i) Name the gas collected at the cathod and
anode respectively.
Q.28
(a) Why cannot a chemical change be normally
reversed?
(ii) Why is the volume of one gas collected
(b) Why is it always essential to balance a
Name this gas?
at one electrode double that at the other?
chemical equation?
(c) Why do diamond and graphite, 2 forms of
carbon evolve different amounts heat on
combustion?
(iii) How will you test the evolved gases?
Q.34
(d) Why does milkness disappear when CO 2
(i) CuSO4 + Zn
is passed throug lime water in excess?
X + YSO4
XSO4 + Y
Y + XSO4
No reaction
(iii) NH4Cl
(a) Can a combination reaction be an oxidation
reaction?
[C.B.S.E. 2011]
Heat
BaSO4 + ZnCl2
NH3 + HCl
(iv) HgCl2 + SnCl2
HgCl2 + SnCl4
(v) 2KClO3
Al2O4 + 2Fe
(vi) 2All + Fe2O3
and of the 2 elements “X” and “Y” which is
more reactive and why?
[C.B.S.E. 2011]
Q.30
ZnSO4 + Cu
(ii) BaCl2 + ZnSO4
(e) Can rusting of Iron take place in distilled
water?
Q.29
Identify the type of reaction[C.B.S.E. 2012]
Q.35
Al2O3 + 2Fe
Balance the following equation [C.B.S.E. 2008]
(i) H2SO4(aq.) + NaOH(aq.)
Na2SO4(aq.) + H2O (l)
(b) How will you test whether the gas evolved
in a reaction is hydrogen?
(ii) KCN(aq.) + H2SO4(aq.)
K2SO4(aq.) + HCN(g)
(c) Why does copper not evolve hydrogen on
reacting with dilute sulphuric acid?
(iv) Al2O3 + H 2SO4
(iii) HgCl2 + SnCl2
(v) Al2(SO 4)3 + NaOH
Hg 2Cl2 + SnCl4
Al2(SO4)3 + H 2SO4
Al(OH)3 + Na2SO4
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CHEMICAL REACTIONS AND EQUATIONS
Q.36
Page # 73
Identify the type of reaction
(i) 2H2O
Elect rolysis
Q.41
2H2 + O 2
2gm of FeSO 4 Crystals were heated in a hard
glass test tube and observations recorded.
(a) What was the successive colour change?
(ii) 2NH3 + H2SO4
(NH4)2SO4
(b) Identify liquid droplets collected on cooler
(iii) AgNO 3 + Nacl
NaNO3 + Agcl
part of test tube.
(iv) Zn(s) + 2AgNO3 (aq.)
Zn(NO3)2(aq.) + 2Ag(s)
(v) Ni(NO3)2(aq.) + 2NaOH(aq.)
Ni(OH)2
(c) What type of odour is observed on heating
FeSO 4 Crystals?
+ 2NaNO3(aq.)
(vi) MgO(s) + C(s)
CO(g) + Mg(s)
Type IV- Thinking Based/Skill Based Questions
Q.37
The marble statues slowly get carroded when
kept in open for a long time. Give suitable
explanation?
Q.38
(a) Based on reactions given below, arrange
the metals invloved in these reactions in
decreasing order of reactivity. Give suitable
explanation.
(i) Zn + CuSO 4
(ii) Cu + 2AgNO 3
ZnSO4 + Cu
Cu (NO3)2 + 2Ag
(i) Zn + FeSO4
ZnSO 4 + Fe
(ii) FE + CuSO4
FeSO 4 + Cu
(b) What is the nature of reactions?
Q.39
A, B and C are 3 elements which undergo
chemical reactions according to following
equations:A 2O3 + 2B
3CSO 4 + 2B
3CO + 2A
B2O3 + 2A
B2(SO4)3 + 3C
A2O3 + 3C
Ans. Following Questions
(a) Which element is more reactive?
(b) Which element is least reactive?
Q.40
You are given following materials:(i) Marble chips (ii) Dil. HCl acid (iii) zinc granules
Identify type of reaction when marble chips
and zinc granules are added separately to acid
taken in two tubes. Write chemical equation
in each case.
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CHEMICAL REACTIONS AND EQUATIONS
EXERCISE – II
Q.1
OLYMPIAD QUESTIONS
The example of a physical change is
Q.7
(A) milk is left at room temperature in summers
(B) an Iron is heated
(C) Iron tawa is left emposed to humid air
(D) Food is cooked
Q.2
Which of the following is/are exothermic
processes
(ii) In beaker “A” and “B” exothermic process
has occurred.
(iii) In beaker A and B endothermic process
has occurred.
(iv) In beaker “C” endothermic process has
occured.
(A) (i) and (ii)
(B) (ii) and (iii)
(C) (iii) and (iv)
(D) (ii) and (iv)
(i) Sublimation of NH4Cl
(ii) Quick lime is added to water
(iii) Evaporation of water
(iv) Dilution of an acid
Q.3
(A) (i) and (ii)
(B) (ii) and (iii)
(C) (iii) and (iv)
(D) (ii) and (iv)
Fe 2O3 + 2Al
Q.8
Example of a chemical change is
(A) fermentation of rice
(B) breathing
(C) curdling of milk
(d) all of above
Q.9
Which of the following is a double displacement
reaction?
Al2O 3 + 2Fe, is a
(i) combination rxn
(ii) Displacement Rxn
(iii) redox Rxn
(iv) Double displacement Rxn
Q.4
(A) (i) and (ii)
(B) (ii) and (iii)
(C) (iii) and (iv)
(D) (ii) and (iv)
(A)
(B)
(C)
(D)
Silver Bromide, On expourse to sunlight turns
grey due to
(A) Formation of silver by its decomposition
Which of the following is not a decomposition
reacion?
(A) CaCO3
CaO + CO2
(B) 2KClO3
2KCl + 3O 2
(C) Digestion of food in the body
(D) H2 + Cl2
2HCl
Q.11
Which of the following represent a double
displacement reaction?
(A) 2H2 + O 2
2H2O
(B) 2Mg + O2
2MgO
(C) AgNO3 + NaCl
AgCl + NaNO3
(D) H2 + Cl2
2HCl
Q.12
Which of the following is a displacement
reaction?
(A) CaCO3
CaO + CO2
(B) CaO + 2HCl
CaCl2 + H 2O
(C) Sublimation of silver Bromide
(D) Decomposition of bromine gas from silver
bromide
Q.6
Water on electrolysis decomposes to hydrogen
and oxygen. the mole ratio of H 2 and O2 is
(A) 1 : 2
(B) 1 : 1
(C) 2 : 1
(D) 4 : 1
Which of the following gases used for storage
of fresh sample of an oil for a long time
(A) Nitrogen and Oxygen
(B) CO 2 and Helium
(C) CO2 and oxygen
(d) Nitrogen and Helium
2H2 + O2
2H2O
FeSO4 + Zn
ZnSO4 + Fe
CH4 + 2O2
2H2O + CO2
Na2SO 4 + Bacl2
BaSO4 + 2Nacl
Q.10
(B) Oxidation of silver Bromide
Q.5
50 ml of water was taken in a beaker A, B
and C. A small amount of CuSO4, NaOH and
NaCl were added to beaker A, B and C
respectively. The temperature of beaker A and
B increased where in beaker c decreases. The
correct statement (s) is/are
(i) In beaker “C” exothermic process has
occurred.
(C) Fe + CuSO4
(D) NaOH + HCl
FeSO4 + Cu
NaCl + H2O
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CHEMICAL REACTIONS AND EQUATIONS
Q.13
The reaction H 2 + Cl2
2HCl is a –
(A) Decomposition reaction
Page # 75
Q.20
Conversion of CaCO3 in to CaO as per following
reaction is an example of –
CaCO3
CaO + CO2
(A) Decomposition reaction
(B) Reduction reaction
(C) Oxidation reaction
(D) None of these
Q.21
Fe 2O3 + 2Al
(B) Combination reaction
(C) Double displacement reaction
(D) Displacement reaction
Q.14
Which of the following is a decomposition
reaction?
(A) NaOH + HCl
is an example of –
(B) NH4CNO
(C) 2KClO 3
2KCl + 3O2
(B) Double displacement reaction
(D) H2 + I2
Q.15
(A) Combination reaction
2HI
(C) Decomposition reaction
(D) Displacement reaction
Which of the following statement is incorrect?
(A) In oxidation, oxygen in added to a substance.
(B) In reduction, Hydrogen is added to a
substance.
Q.16
Q.22
(A) SO2
(B) H2S
(D) Reducing agent is oxidized.
(C) H2O
(D) S
Which of the following is a combustion reaction–
Q.23
(C) Burning of petrol
What happens when dil hydrochloric acid is
added to iron fillings?
(D) None of these
(B) Chlorine gas and Iron hydroxide are
produced.
Which of the following is a redox reaction?
(C) NO reaction takes place
(A) CaCO3
(D) Iron salt and water are produced.
CaO + CO2
(B) H2 + Cl2
(C) CaO + 2HCl
2HCl
(D) NaOH + HCl
CaCl2 + H2O
Q.24
NaCl + H2O
Which statement is correct about the following
reaction?
ZnO + CO
When Iron nails are added to an aquous solution
of copper sulphate, a chemical change occurs,
which of the following is not true about this
reaction?
(A) Blue colour of the solution fades.
(B) Iron nails becomes brownish in colour.
Zn + CO2
(A) ZnO is being oxidized
(C) It is a displacement reaction.
(B) CO is being reduced
(D) Iron nails dissolves completly.
(C) CO 2 is being oxidized
(D) ZnO is being reduced
Q.19
2H2O + 3S the
(A) Hydrogen gas and Iron chloride are
produced.
(B) Melting of wax
Q.18
In reaction SO2 + 2H2S
reducing agent is –
(C) Oxidizing agent in oxidized.
(A) Boiling of water
Q.17
Al2O3 + 2Fe This reaction
NaCl + H2O
H2NCONH2
The reaction C + O 2
CO2 + Heat is a –
(A) Combination reaction
(B) Oxidation reaction
(C) Exothermic reaction
(D) All of the above
Q.25
Pot assium rea ct s wi th bromine t o form
potassium bromide.
[NTSE]
(A) 2K + Br
2KBr
(B) K2 + Br2
2 KBr
(C) K 2 + Br2
(D) K2 +Br2
KBr2
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Q.26
Q.27
CHEMICAL REACTIONS AND EQUATIONS
A silver spoon on exposure to air reacts with
the sulphur present in air to give a black material
called ______.
[NTSE]
(A) Silver oxide
(B) Silversulphide
(C) Tarnish
(D) Coal tar
In the decomposition of sulphates by heat,
which is the gas formed exclusively along with
the metal oxide?
Q.28
Q.33
The rate of a chemical reaction is altered by
______.
[NTSE]
(A) nature of reactants
(B) changing temperature
(C) using a catalyst
(D) all the above
Q.34
Which of the following is an example of a
reversible reaction?
[NTSE]
[NTSE]
(A) SO2
(B) SO3
(C) SO3 and SO2
(D) H2SO3
[NTSE]
Q.36
When hydrogen sulphide gas is passed through
a blue solution of copper sulphate, a black
precipitate of copper sulphide is obtained and
the sulphuric acid so formed remains in the
solution. The reaction is an example of
(A) a combination reaction
[NTSE]
(B) a displacement reaction
(C) a decomposition reaction
(D) a double decomposition reaction
Q.37
In the following equations
Na2CO3 + xHCl
2NaCl + CO2 + H2O the
value of x is:
[NTSE]
(A) 1
(B) 2
(C) 3
(D) 4
Q.38
Combustion of fuel is
(A) displacement reaction
(B) double displacement reaction
(C) oxidation reaction
(D) isomerisation reaction
Q.39
The reaction between acid and base to form
salt and water is an example of
[NTSE]
(C) Liquefaction of gases to liquids
(D) Decay of matter
Which among the following reactions are
exothermic in nature?
[NTSE]
(A) Bond formation
(B) Bond breaking
(C) Combustion of carbon
(D) Both (A) and (C)
The reaction P4 + 3O2
(A) synthesis reaction
2P2O3 is ____.
[NTSE]
(B) displacement reaction
(C) decomposition reaction
(D) combustion
Q.32
CaO + CO2
AgCl + KNO3
NaCl + H 2O
Which of the following reaction will not take
place?
[NTSE]
(A) Zn + FeSO4
ZnSO4 + Fe
(B) 2Kl + Cl2
2KCl + I2
(C) Zn + MgSO4
ZnSO4 + Mg
(D) Mg + CuSO4
MgSO4 + Cu
(B) Vapourisation of liquids to gases
Q.31
(B) CaCO3
(C) AgNO3 + KCl
(D) NaOH + HCl
Fe3O4 + 4H2
Q.35
(A) Melting of solids to liquids
Q.30
1237 K
Which among the following is not a physical
change?
Q.29
(A) 3Fe + 4H2O
PbO 2 + 4HCl
PbCl2 + 2H 2O + Cl2. The
substance undergoing oxidation is _____.
[NTSE]
(A) lead dioxide
(B) hydrochloric acid
(C) hydrogen
(D) lead chloride
In the equation FeCl 3 + xNaOH
yNaCl +
Fe(OH) 3, the value of x and y, respectively,
are _____.
[NTSE]
(A) 3 and 1
(B) 3 and 3
(C) 2 and 3
(D) 3 and 4
[NTSE]
(A) decomposition reaction
(B) combination reaction
(C) displacement reaction
(D) double displacement
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CHEMICAL REACTIONS AND EQUATIONS
Q.40
Page # 77
Which of the following reactions are exothermic
in nature?
Q.47
[NTSE]
FeSO4 + Cu
(A) Combustion of Carbon
FeSO4 + Zn
ZnSO4 + Fe
(B) Bond breaking
(A) Zn is most reactive, Fe is least reactive
(B) Fe is most reactive and cu is least reactive
(C) Zn is most reactive and cu is least reactive
(D) Cu is most reactions, Fe is least reactive
(D) Both (A) and (C)
Which of the following changes is not a physical
change?
[NTSE]
Q.48
Choose the incorrect statement.
[NTSE]
(A) physical change is reversible
(A) glowing of filament in bulb
(B) physical change results information of new
substances
(B) combustion
(C) chemical change is permanent
(C) boiling of water
(D) physical change is accompanied by energy
change
(D) sublimation
Q.42
[NTSE]
CuSO 4 + Fe
(C) Bond formation
Q.41
Consider the reactions
The substance that looses electrons is called
as:
[NTSE]
(A) oxidizing agent
(B) reducing agent
(C) catalyst
(D) none of above
Q.49
Which of following is fast reaction? [NTSE]
(A) reaction between H 2 and O2 to form H2O
(B) reaction between acid and base to form
salt and water
(C) hydrolysis of ester
(D) hydrolysis of sugar to glucose
Q.43
The process of reduction involves
[NTSE]
(A) removal of hydrogen
(B) gain of electrons
(C) addition of oxygen
(D) loss of electrons
Q.44
In the reaction H2S + Cl2
oxidizing agent is:
(A) H2S
(C) HCl
Q.45
2HCl + S, the
[NTSE]
(B) Cl2
(D) S
Select Redox reaction from the following
(A) Zn + CuSO4
(B) CaO + 2HCl
ZnSO4 + Cu [NTSE]
CaCl2 + H 2O
(C) NaOH + 2HCl
NaCl2 + H 2O
(D) CaCO3
CaO + CO2
Q.46
Which of the following reactins is not correct?
[NTSE]
(A) 2AgNO 3 + Cu
Cu(NO3)2 + 2Ag
(B) Cl 2 + 2KI
2KCl + I2
(C) FeSO4 + Cu
CuSO4 + Fe
(D) CuSO4 + Zn
ZnSO4 + Cu
ANSWER KEY
1.
C
2.
D
3.
B
4.
A
5.
C
6.
D
7.
D
8.
D
9.
D
10.
D
11.
C
12.
C
13.
C
14.
C
15.
C
16.
C
17.
B
18.
D
19.
D
20.
A
21.
D
22.
B
23.
A
24.
D
25.
A
26.
B
27.
B
28.
D
29.
D
30.
D
31.
B
32.
B
33.
D
34.
A
35.
C
36.
D
37.
B
38.
C
39.
D
40.
D
41.
B
42.
B
43.
B
44.
B
45.
A
46.
C
47.
C
48.
B
49.
B
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Page # 78
NUTRITION
1. NUTRITION
The whole process by which an organism
obtains its food is referred to as nutrition.
NUTRITION
It is the method of obtaining nutrients from the environment. It can be defined as the process by
which the organism ingests, digests, absorbs, transports and utilises nutrients and disposes off their
end products.
NUTRIENT
The different component of food that have distinct functions like providing energy. materials for body
building, maintenance & regulation of metabolism are called nutrient.
For exmple-Proteins, Minerals, Vitamin, Carbohydrates, fats.
MODES OF NUTRITION
Mode of nutrition
Autotrophic nutrition
Heterotrophic nutrition
Holozoic
nutrition
Saprotrophic
nutrition
Pasrsitic
nutrition
(a) Autotrophic Nutrition
In this type of nutrition, organisms synthesise the organic materials they require from inorganic sources.
All green plants are autotrophic and use light as a source of energy for the synthesis.
Autotrophs
The organisms which make their own food from carbon dioxide and water in the presence of sunlight
and chlorophyll are called autotrophs. These organisms are also called producers and include green
plants and some bacteria.
PHOTOSYNTHESIS
It is the process by which green parts of the plant synthesise organic food in the form of carbohydrates
from CO2 and water in the presence of sunlight.
6CO2 + 6H2O
light
chlorophyll
C6H12O6 + 6O2
In plants and most algae it occurs in the chloroplasts and there are two principal reactions:
(i) Light reaction (light-dependent) requires the presence of light energy from sunlight which is obtained
by photosynthetic pigments, i.e., chlorophyll and used to bring about the photolysis of water.
H2O
2H+ + 2e-
(ii) Dark reaction (light-independent) i.e., this reaction is not dependent on light and during this
reaction carbon dioxide is reduced to carbohydrate in a metabolic pathway known as the Calvin cycle.
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NUTRITION
Difference between light and dark reactions
Features
Requirement of light
Required
Light reaction
Takes place inside
Grana part of the chloroplast
ATP and NADPH2
ATP and NADPH2 are produced
by the conversion of light energy
into chemical energy
Sugar formation
Release of oxygen
No sugar formation takes place
Oxygen is released
Dark reaction
Not required
The stroma region of
chloroplast
ATP and NADPH2 formed
during light reaction are
used for the fixation of
CO 2 into carbohydrate
Sugar formation takes
place
No oxygen is released
VARIOUS COMPONENTS OF PHOTOSYNTHESIS
Various components necessary for the process of photosynthesis are :
1.Chlorophyll
2. Carbon dioxide
3. Sunlight
4. Water
This can be demonstrated with the help of various experiments.
1. Chlorophyll
Chlorophyll is green pigment present in the green leaves.
Activity-1.1
SCIENCE COMES ALIVE
To prove that chlorophyll is essential for photosynthesis.
Apparatus
Plant with variegated leaves, Apparatus for starch test i.e., iodine solution, beaker, test tubes.
BLUE BLACK
(STARCH)
GREEN
(CHLOROPHYLL)
NON-GREEN
COLOURLESS
(NO STARCH)
Fig. 1 Apparatus to show that chlorophyll is essential for phtosynthesis
Procedure
1. A potted plant with variegated leaf (Coleus, Croton) is kept in darkness for two days to make the
leaves starch-free.
2. A plant is then kept in sunlight for few hours.
3. A leaf is removed from the plant and tested with iodine for starch, after decolourising it first with
water and then alcohol.
Conclusion
It is seen that the portions of leaves which are devoid of chlorophyll remain colourless (starch free)
whereas the rest of the leaf turns blue-black due to the presence of starch.
PRACTICE ZONE
1.1
1. Why do plants need magnesium ?
2. What type of the plants do we use in the experiment to prove that chlorophyll is necessary for
photosynthesis.
3. What substance does a plant need to be able to convert glucose into proteins ?
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NUTRITION
2. Carbon-Dioxide
Photosynthesis has been found to takes place in a very wide range of CO2 concentration.
Within the range the rate of photosynthesis will decrease or increase with decrease or increase in
CO2 concentration, provided other factors are not limiting.
Relatively high concentration of CO 2, reduces the rate of photosynthesis and if given for a
considerable period of time, has detrimental effect on the process itself.
Activity-1.2
SCIENCE COMES ALIVE
To prove that carbon dioxide is necessary for the process of photosynthesis.
Apparatus
Two healthy potted plants, Potassium hydroxide (KOH), 2 bell jars, watch-glass, vaseline, 2 glass
plates, Iodine solution, H2O and alcohol.
Procedure
1. Take two healthy potted plants of same size.
2. Destarch them by keeping in a dark room for 3-4 days.
3. Now place these potted plants on separate glass sheets.
4. Place watch glass containing KOH by the side of one of the plants. KOH has the property to absorb
carbon dioxide.
5. Now cover these potted plants with bell jars.
6. To make the apparatus air tight use vaseline to seal the botton of the jars to glass plates.
7. Keep this experimental setup in sunlight for 3 to 4 hours.
8. Pluck one leaf from each plant.
POTTED PLANT
BELL JAR
BELL JAR
WATCH-GLASS
CONTAINING
KOH
NO WATCH-GLASS
CONTAINING KOH
A
B
GLASS SHEET
Fig. 2 Apparatus to show that CO2 is necessary for the process of photosynthesis
9. Perform starch test for both the leaves by decolourizing leaf first in water, then in alcohol and
finally testing with iodine solution.
10. Leaf which was within bell jar with KOH solution gives a negative test whereas other one gives
positive test.
Conclusion
The experiment clearly proves the fact that carbon dioxide is absolutely essential for photosynthesis.
The part of the leaf which could not show iodine test positive or manufacture starch had all the
requirements for photosynthesis except CO 2, which was absorbed by KOH in the bottle.
ON
YOUR
TIPS
The light intensity where in the
photosynthesising organs neither takes
CO2 nor release the same is called
compensation point.
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NUTRITION
3. Sunlight
Activity-1.3
SCIENCE COMES ALIVE
To prove that light is necessary for photosynthesis-Starch Printing Test.
Apparatus
Ganong's light screen or two strips of black paper. A destarched plant, Apparatus for starch test.
Procedure
1. Take a Ganong's light screen. It has a small metallic box with ventilating holes. To the is attached
a spring handle, bearing a lid at its one end which fits over the metallic box lightly.
The lid has a design within its centre. You can even use two black paper strips to cover the leaf.
2. A potted plant is kept in the dark for two days to make the leaves starch free.
3. A leaf is partly covered with a piece of black paper or by a Ganong's light screen.
4. The pot is then kept in the sunlight for few hours.
5. The leaf is then tested with jodine solution for starch.
Conclusion
It is seen that the starch is formed only in the exposed portion of the leaf whereas covered portion
remains starch-free because light was not available to such patches for photosynthesis.
STARCH FORMED
BLACK PAPER
NO STARCH
FORMATION
Fig. 3 Apparation to show that light is required for phtosythsis
PRACTICE ZONE
1.1
1. Plants need magnesium to make chlorophyll.
2. Desarched potted plants with variegated leaves eg. Croton and Pothos.
3. Nitrogen.
4. Water
Plants absorb water from the soil with the help of root system. The effect of water deficiency on
the rate of photosynthesis is indirect one.
Decrease in H2 O content of the leaves may cause partial or complete closure of stomatal opening,
and hence a reduction in the rate of diffusion of CO2 .
A partial drying of the cell walls cause decrease in its permeability to CO2 , Another indirect effect of
water deficiency is that the accumulation of sugar within the cells increases the rate of respiration
and thus decreases apparent photosynthesis
(b) Heterotrophic Nutrition
The type of nutrition in which organisms derive their food (nutrients) from other living organisms. In
heterotrophic nutrition, the energy is derived from the intake and digestion of the organic substances,
normally of plant or animal tissue. Heterotrophic mode of nutrition are of different types :
(i) Saprotrophic Nutrition
It refers to the mode of nutrition in which organisms obtain nutrients from the dead and decaying
organic matter, e.g., fungi, yeast and bacteria are called saprophytes.
(ii) Parasitic Nutrition
It refers to the mode of obtaining food synthesised by others. The organism which obtains food is
called the ‘parasite’ and the organism from which food is absorbed is called the ‘host’. This nutrition is
observed in fungi, bacteria, a few plants like Cuscata and some animals like Plasmodium and roundworm.
(iii) Holozoic Nutrition
It refers to the mode of nutrition in which the complex organic matter in the form of solid food is
ingested, digested and then absorbed into the cells and utilised, e.g. amoeba, frog, human beings.
Heterotrophs
The organisms which cannot make their food and depend directly or indirectly on autotrophs for their
survival are called heterotrophs. These organisms include animals and fungi.
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TYPE OF HETEROTROPHIC NUTRITION
1. Saprophytic or Saprotrophic Nutrition :
It is a mode of heterotrophic nutrition in which food is obtained from organic remains like dead
organisms, excreta, fallen leaves, broken twigs, food articles, etc. Organisms performing saprophytic
nutrition are called saprophytes.
·
2. Parasitic Nutrition :
It is a mode of hetrotrophic nutrition in which a living organisms flourishes by obtaining food from
another living organism. The lving organisms which obtains food and shelter from another organism is
called parasite. The organism which provides food and shelter to a parasite is known as host. An
external plant parasite is Cuscuta (Amarbel). It is a non-green plant that sends haustroria or sucking
roots into host plant for obtaining food and water.
3. Holozoic Nutrition :
It is a mode of heterotrophic nutrition which involves intake of solid pieces of food. Since solid food is
taken in, holozoic nutrition is also called ingestive nutrition. The food may consist of another animal,
plant or its parts. Depending upon the source of food, holozoic organisms are of three types –
Herbivores, carnivores, omnivores.
Herbivores :
(L.herba-plant, vorare-to eat)
They are holozoic organisms which feed on plants or plant parts, e.g., Cow, Buffalo, Deer, Goat, Rabbit,
Grasshopper, Elephant, Squirrel, Hippopotamus.
Carnivores :
They are animals which feed on other animals. Carnivores are also called predators they hunt, kill and
feed on their preys, e.g. Lion, Tiger, Leopard, Snake, Hawk.
Omnivores :
(L.omnis-all, vorare-to eat)
They are holozoic organisms which feed on both plant and animal materials, e.g. Cockroach, Ant, Pig,
Crow, Rat, Bear, Dog, Humans.
NUTRITION IN AMOEBA
Protozoan protests carry out holozoic nutrition through intracellular digestion.
Fig. - 4 Nutrition in Amoeba
ON
YOUR
TIPS
Free-living platyhelminthes
(e.g., planaria) possess both
kinds of digestion. Humans
have extracellular digestion.
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NUTRITION
Some protests can ingest food particle from any point on the surface (e.g., Amoeba) while others have
fixed points for the same (e.g., Paramoecium). Protozoans like Amoeba capture food with the help of
temporary finger-like processes called pseudopodia. Protozoans like (Paramoecium have small hair-like
processes called cilia.) Beating of cilia creates current in water that pushes food particle through
cytostome or cell mouth. The process of ingestion of solid food particle by a cell or unicellular organism
is called phagocytosis.
As soon as Amoeba comes in contact with a food particle or prey, it throws pseudopodia all around the
same. The tips of encircling pseudopodia fuse and the prey comes to lie in a vesicle or phagosome. This
method of intake of food is called circumvallation. Amoeba can also ingest food by other methods like
import, circumfluence and invagination.
DIGESTIVE SYSTEM OF HUMAN
The organs which are responsible for ingestion, digestion, absorption, assimilation and egestion constitute
the digestive system. The digestive system comprises of the alimentary canal and associated digestive
glands.
Digestive system
Alimentary canal
Mouth
Buccal
cavity
Oesophagus
Digestive Glands
Stomach
Intestine
Small Intestine
Duodenum Jejunum
Large Intestine
lluem
Caecum
Colon
Rectum
(A) Alimentary canal
The alimentary canal is basically a long tube extending from the mouth to the anus.
It is differentiated into following parts.
(i) Mouth
It is a transverse slit bounded by movable lips. The lips serve to close and open mouth. holding the
food in between and also help in speaking.
The floor of the buccal cavity has a tongue bearing taste buds. Man possess teeth on both the jaws.
There are 32 teeth of four different types, namely incisors, canines, premolars and molars.
Digestion may be intracellular (Paramoecium) or extracellular (multicellular animals).
The process of digestion starts in the mouth cavity and continues upto the intestine.
In the mouth, food gets mixed up with saliva secreted by salivary glands.
Saliva contains an enzyme ptyalin which breaks polysaccharide starch into disaccharide maltose.
Starch
Ptyalin
( Salivary amylase)
Maltose
The food from the mouth cavity passes into the stomach through the oesophagus.
ON
YOUR
TIPS
Apart from the presence of food,
the sight, smell or even touch of
one's favourite food can initiate
secretion of gastric juices.
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(ii) Pharynx
It is a short, conical region that lies after the mouth cavity. The pharynx are divided into two parts —
the nasopharynx which lies behind the nasal cavities and the oropharynx which lies behind the mouth.
(iii) Oesophagus (food pipe)
It is a long, narrow, muscular tube which leads to the stomach, The oesophagus is a collapsible muscular
tube leading from pharynx to stomach. There are no digestive glands but mucus glands are present.
(iv) Stomach
It is a thick, muscular and J shaped sac present on the left side of upper part of abdomen. Gastric
glands are present in the wall of stomach. These releases gestric juice or digestive juice, which
contains mucus. hydrochloric acid and a protein digesting enzyme called pepsin.
Mucus lubricated the food and protects the inner linning of the stomach from the action of HCl.
HCl creates an acidic medium, which facilitates the action of enzyme pepsin and kills the bacteria
present in food.
Pepsin breaks down proteins into peptides.
Sphincter muscles regulate the exit of food from stomach into intestine due to peristaltic waves of
stomach.
Fig. -5 Human alimentary canal
(v) Intestine
It is the largest part of alimentary canal which is fitted into a compact space because of extensive
coiling. It is distingushed into small intestine and large intestine.
Small intestine
The small intestine is the site of the complete digestion of carbohydrates. proteins and fats.
It receives the secretions of the liver and pancrease for digestion.
Food is mixed with three digestive juices (bile juice, pancreatic juice and intestinal juice)
Bile juice (from the liver) provide alkaline medium and emulsifies fats (conversion of larger fat globules
into smaller fat droplets) but it is non enzymatic digestive juice so has no chemical action on food.
Pancreatic juice (from the pancreas) contains trypsin, pancreatic amylase and pancreatic lipase
enzymes which digest the peptons, starch and fats into peptides, maltose and fatty acids and glycerol
respectively.
The wall of intestine secretes intestinal juice which contains enzymes for complete digestion of proteins
into amino acids, carbohydrates into glucose and fat into fatty acid and glycerol.
The inner lining of the small intestine has numerous finger like projections called villi which increase the
surface area for absorbtion of digested food.
These are richly supplied with blood vesseles.
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NUTRITION
Large Intestine
It is much shorter and wider than small intestine and is differentiated into three regions viz., caecum,
which is small rounded blind sac from which vermiform appendix arises; colon is the inverted U-shaped
tube and the rectum opens to exterior through anus.
(vi) Anus
The rest of the material is removed from the body via anus. The exit of waste material is regulated by
anal sphincter.
(B) Digestive Glands
Various glands associated with alimentary canal are :
Fig. -6 Salivary glands of man
ON
YOUR
TIPS
On eating food of our interest, watering
starts in our mouth. This water is
basically the saliva which is secreted
by salivary glands that get activated
by eating and even seeing or thinking of
good food.
(i) Salivary Glands
The salivary glands secrete the first of the digestive juices, the saliva. There are three pairs of salivary
glands, namely the parotids, sub-maxillary and sublingual glands.
(ii) Gastric Glands
They are branched tubular glands which lie in the mucus membranes of the stomach. They secrete
gastric juice, which is clear, acidic containing HCl, enzymes and mucus.
(iii) Liver
It is the largest gland in man and lies below diaphragm in the right upper part of abdomen. Liver comprises
of two lobes, right and left, where the right lobe is much larger than the left lobe. The cells of liver, i.e.,
hepatic cells produce bile juice which flows out of liver through hepatic ducts forming common bile duct
and opens into duodenum. Bile juice then flows into gall bladder through the cystic ducts.
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NUTRITION
Fig. -7 Liver and Pancreas and their ducts
(iv) Pancreas
It is a soft lobulated gland present in between the loops of duodenum. It secretes pancreatic juice
containing enzymes which is poured into duodenum with the help of pancreatic duct.
Table: Summary of the digestive enzymes of various glands with their secretions and end products of
Digestion in Man
Se cretio
n
ON
YOUR
TIPS
It is the tooth decay which involves
destruction of the enamel layer of the
tooth by acids produced by the action
of bacteria on sugar. If dental caries is
not treated, it can spread to the dentine
and pulp of the tooth, causing inflammation
a n d i n f e c t io n o f t h e to o th .
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NUTRITION
N.C.E.R .T TEXT BOOK SOLUTION
Q.1
Why is diffusion insufficient to meet the oxygen requirement of multicellular organisms like humans?
Ans.
In humans, the body organisation is multicellular and complex. The living cells are not in direct constant
with environment because they are generally covered by dead cells. Air containing intracellular spaces
are also absent so quick diffusion cannot occur. Cell to cell diffusion is very slow process and if it takes
place in humans then passage of oxygen in whole body will take about years. Thus, diffusion is
insufficient to deliver oxygen to all parts of a multicellular organisms like humans.
Q.2
What criteria do we use to decide whether something is alive?
Ans.
The main criterion that is used to decide whether something is alive, is movement. Movements may be
of different types like locomotion (running, walking), moving body parts, breathing movements, growth
movements and movement of molecules in various metabolic reactions. Besides movements, other
qualities found in living beings are self-built body organisation, presence of protoplasm, self repair,
various vital life processes like metabolism, growth, nutrition, respiration, excretion and reproduction.
All living organisms have a definite lifespan and particular life cycle.
Q.3
What processes would you consider essential for maintaining life?
Ans.
The processes essential for maintaining life are nutrition, metabolism, respiration, circulation/transportation and excretion.
Q.4
What are the differences between autotrophic nutrition and heterotrophic nutrition?
Ans.
In autotrophic mode of nutrition, organisms (green plants, some protists and bacteria) prepare their
own food from inorganic raw materials with the help of energy obtained from sunlight whereas in
heterotrophic mode of nutrition, organisms obtain food prepared by autotrophs or from other organic
sources as they cannot synthesise their own food. Heterotrophic nutrition may be saprophytic,
parasitic and holozoic.
Q.5
Where do plants get each of the raw materials required for photosynthesis?
Ans.
The raw materials required for photosynthesis are carbon dioxide and water. Plants obtain water from
the soil through roots and carbon dioxide from the atmosphere through stomata present on leaves.
Q.6
What is the role of the acid in our stomach?
Ans.
Hydrochloric acid (HCl) is secreted inside the stomach. The main functions of HCl are to
(i) stop the action of salivary amylase
(ii) kill the microbes present in the food
(iii) provide acidic medium necessary for the activation of the enzyme pepsin
(iv) make food soft
(v) convert pepsinogen and prorennin into active forms of pepsin and rennin.
Q.7
What is the function of digestive enzymes?
Ans.
Digestive enzymes are hydrolytic in nature which help in digestion of carbohydrates, proteins and fats.
They bring about hydrolytic splitting of complex organic substances into simple soluble and absorbable
substances. For example, by the action of digestive enzymes, proteins are converted into amino acids.
Q.8
How is the small intestine designed to absorb digested food?
Ans.
Small intestine is a long, tubular structure. Its inner wall is lined by epithelium which possess numerous
finger-like projections called villi. These villi not only increase the surface area for absorption but also
reach deep into the lumen of intestine for maximum absorption of digested food. Villi possess blood
capillaries and lymph vessels (lacteals) for quick transport of absorbed food.
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NUTRITION
EXERCISE – I
Q.1
PRACTISE FOR FORMATIVE ASSESSMENT
CO2 and O2 balance in atmosphere is due to
(A) Photorespiration (B) Photosynthesis
Q.2
Q.3
(A) Water
(B) Carbon dioxide
(C) Both from water and carbon dioxide
(D) Oxygen in air
With regards to natural eating habits, a human is
Q.8
(B) Deglutition
(C) Peristalsis
(D) Churning
(B) Stomach
(C) Duodenum
(D) Mouth
(B) Ptyalin
(C) Trypsin
(D) Rennin
Pepsin digests
(A) Proteins in stomach
(B) Carbohydrates in duodenum
(C) Proteins in duodenum
(D) Fats in ileum
If the stomach did not produce any hydrochloric acid, which enzyme will not function ?
(A) Ptyalin
Q.9
(D) A Granivore
Saliva has the enzyme
(A) Pepsin
Q.7
(C) An omnivore
Which of the following regions of the alimentary canal of man does not secrete a digestive enzyme ?
(A) Oesophagus
Q.6
(B) A carnivore
Muscular contractions of alimentary canal are
(A) Circulation
Q.5
(D) Leaf anatomy
During photosynthesis the oxygen in glucose comes from
(A) An herbivore
Q.4
(C) Respiration
(B) Trypsin
(C) Pepsin
(D) Collagenase
(C) In liver
(D) In spleen
(C) Pituitary
(D) Thyroid
Chief function of bile is
(A) To digest fat by enzymatic action
(B) To emulsify fat for digestion
(C) To eliminate waste product
(D) To regulate process of digestion
Q.10
Where is bile produced ?
(A) In gall bladder
Q.11
Largest gland in human body is
(A) Liver
Q.12
(B) In blood
(B) Pancreas
The original function of the vertebrate stomach was
(A) Storage
(B) Digestion
(C) Enzyme secretion
(D) Absorption
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NUTRITION
FILL IN THE BLANKS
1.
The whole process by which an organism obtains its food is referred to as .............
2.
Other term for autotrophic nutrition is ..............
3.
.................. manufacture their food from inorganic substances in the presence of energy derived
from the oxidation of simple inorganic compounds of iron, sulphur etc.
4.
The process of utilization of absorbed food is known as ..............
5.
Those organisms which depend on faecal matte of other organisms are known as ...............
6.
Ligth reaction is also known as ............. phase.
7.
The light intensity, at which the photosynthetic intake CO 2 is called .............. .
8.
Ingestion of food in Amoeba takes place by the process of ............
9.
................ is the type of digestion that occurs inside the lumen of digestive tract.
10.
................ are known as suicide bags of the cell.
ANSWER KEY
1.
B
2.
A
3.
C
4.
C
5.
A
8.
C
9.
B
10.
C
11.
A
12.
A
6.
B
7.
A
3.
Chemoautotrophs
8.
Phagocytosis
FILL IN THE BLANKS
1.
Nutrition
2.
a
4.
Assimilation
5.
Coprozoic heterotrophs
6.
Photochemical phase
7.
Compensation point
9.
Intercellualr
10.
Lysosomes
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EXERCISE – II
NUTRITION
PRACTISE FOR SUMMATIVE ASSESSMENT
Very Short Answer Type Questions
Q.1
Define heterotrophic nutrition.
Q.2
What are heterotrophs ?
Q.3
Which types of organisms are called consumers ?
Q.4
What is saprophytic nutrition ?
Q.5
Define saprophyte.
Q.6
Define a hervivore.
Q.7
What is carnivore ?
Q.8
Which type of animal is called omnivore ?
Q.9
What is the mode of nutrition in Amoeba ?
Q.10
What type of digestion occurs in Paramoecium ?
Short Answer Type Questions
Q.11
How do saprophytic organisms obtain their nourishment ?
Q.12
What is the importance of saprophytes ?
Q.13
What is the action of hydrochloric acid of gastric juice ?
Q.14
Name a digestive juice that has no enzymes. What is the role of this juice ?
Q.15
Name the various parts of large intestine. What is the role of large intestine ?
Long Answer Type Questions
Q.16
Explain the mechanism of nutrition of Amoeba with the help of suitable diagram.
Q.17
Describe the various types of heterotrophic nutrition.
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REAL NUMBERS
Page # 91
REAL NUMBERS
1.1
BASIC CONCEPTS AND IMPORTANT RESULTS
(a) Natural numbers : Counting numbers are called natural numbers. We start counting from 1, so 1
is the smallest natural number. A set of natural numbers is denoted by N. Thus,
N = {1, 2, 3, ...up to the numbers as possible as we can count}
(b) Whole numbers : Natural numbers together with zero are called whole numbers. A set of whole
numbers is denoted by W. Thus,
W = {0, 1, 2, 3, .....}
All natural numbers are whole numbers but all whole numbers are not natural numbers. Only the
difference between whole numbers and natural numbers is the number zero (0).
(c) Integers : All positive and negative natural numbers together with zero are called integers. A set
of integers denoted by Z or I. Thus,
Z = {.... – 6, – 5, – 4, –3, – 2, –1, 0, 1, 2, 3, 4, 5, 6 ....}
(d) Rational numbers :
A number of the form
rational number. For example,
p
, where p and q are integers and q
q
0 is called a
2
3
,
, 2, 0, etc., are rational number..
7
8
The decimal expansion of a rational number is either terminating or non-terminating repeating one.
(e) Irrational numbers : A number which is not a rational number, i.e., which cannot be written in
the form
p
, p and q
q
2 , – 3, 7 5,
Z or I and q
1
2,1+
0, is known as an irrational number. For example,
6 , etc., are irrational numbers.
The decimal expansion of an irrational number is non-terminating and non-repeating one.
(f) Real numbers : All rational and irrational numbers together make up a collection, called real
numbers.
Note : All natural numbers, integers, rational numbers and irrational numbers are real numbers.
1.2
EUCLID’S DIVISION ALGORITHM OR EUCLID’S DIVISION LEMMA
For any two given positive integers a and b, there exist unique whole numbers q and r such that:
a = b × q + r, where 0
r<b
2
5
4
1
2
Here, a is called the dividend, b the divisor, q the quotient and r is called the remainder. For example,
when we divide 5 by 2, we get 2 as quotient and 1 as remainder
Here 5 = 2 × 2 + 1
Dividend = Divisor × Quotient + Remainder
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REAL NUMBERS
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Properties of Euclid’s Division Lemma :
(i) If an integer c be a divisor of each of the two given integers a and b, then we say that c is a
common factor of both a and b.
(ii) Let P be a prime number and if a,b, are integers such that
P
P
P
, then either
or
is a factor..
ab
a
b
Note : If a prime number divides a product of integers, then it necessarily divides either of the
integers.
Obtaining HCF by Euclid Division Lemma :
Let a and b be two positive integers. If a = b × q + r, 0
r <b
Then HCF (a, b) = HCF (b, r)
where HCF(a, b) = Common division of a and b and
HCF (b, r) = Common division of b and r.
1.3
FUNDAMENTAL THEOREM OF ARITHMETIC
Every composite number can be expressed as a product of primes and this factorization is unique,
apart from the order in which the prime factors occur.
Note : Any number of the form an will end with the digit zero if prime factors of an would contain
5 and 2 as a prime factor, where n
W.
1.4
THEOREMS ON RATIONAL NUMBERS
(i)
Let x be a rational number whose decimal expansion terminates. Then x can be expressed in the form
p
n m
q , where p and q are co-prime, and the prime factorization of q is of the form 2 5 , where n, m are
non-negative integer.
(ii)
p
Let x = q be a rational number, such that the prime factorization of q is of the form 2n5 m , where n,
m are non-negative integers. Then x has a decimal expansion which terminates.
(iii)
p
Let x = q be a rational number such that the prime factorization of q is not of the form 2n5m, where
n, m are non-negative integers. Then x has a decimal expansion which is non-terminating repeating
(recurring).
Note : HCF(p, q, r) × LCM(p, q, r)
(p × q × r), where p, r and q are positive integers.
p× q×r.HCF(p, q,r)
LCM(p, q, r) = HCF(p, q).HCF(q,r).HCF(p,r)
p × q×r.LCM(p, q,r)
HCF(p, q, r) = LCM(p,q).LCM(q,r).LCM(p,r)
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REAL NUMBERS
Page # 93
SOLVED PROBLEMS
Ex.1
Sol.
Show that any positive odd integer is of the form 6q + 1, or 6q + 3 or 6q + 5, where q is some integer.
Let us start with taking a, where a is any positive odd integer. We apply the division algorithm, with a
and b = 6. Since 0 r < 6, the possible remainders are 0, 1, 2, 3, 4, 5. That is, a can be 6q or 6q + 1,
or 6q + 2, or 6q + 3, or 6q + 4, or 6q + 5, where q is the quotient. However, since a is odd, we do not
consider the cases 6q, 6q + 2 and 6q + 4 (since all the three are divisible by 2). Therefore, any
positive odd integer is of the form 6q + 1, or 6q + 3, or 6q + 5.
Ex.2
Sol.
If a = 10 and b = 3. Then find q and r such that a = bq + r, o
Clearly 10 = 3 × 3 + 1
q = 3 and r = 1 are required numbers.
Ex.3
Sol.
Use Euclid’s division algorithm to find the HCF of 135 and 225.
We start with the larger integer, that is, 225. Then by Euclid’s division algorithm we get:
225 = 135 × 1 + 90
Now, consider the divisor 135 and the remainder 90 and apply the division algorithm again,
we get :
135 = 90 × 1 + 45
Now, consider the divisor 90 and the remainder 45 and apply the division algorithm again, we get.
90 = 45 × 2 + 0
Notice that the remainder has become zero and we cannot proceed any further. The HCF of 90 and 45
is 45 and we claim that the HCF of 225 and 135 is also 45.
Ex.4
An army contingent of 616 members is to march behind an army band of 32 members in a parade. The
two groups are to march in the same number of columns. What is the maximum number of columns in
which they can march?
Hint : Find HCF of 616 & 32
Sol.
Ex.5
Sol.
Ex.6
Sol.
r < b.
Use Euclid's division lemma to show that the square of any positive integer is either of the form 3m or
3m + 1 for some integer m.
Let a be any odd positive integer. We apply the division lemma with a and b = 3.
Since 0 r < 3, the possible remainders are 0, 1 and 2. That is, a can be 3q, or 3q + 1, or
3q + 2, where q is the quotient.
Now, (3q)2 = 9q2
which can be written in the form 3m, since 9 is divisible by 3.
Again, (3q + 1) 2 = 9q 2 + 6q + 1 = 3 (3q2 + 2q) + 1
which can be written in the form 3m + 1 since 9q 2 + 6q, i.e., 3(3q2 + 2q) is divisible by 3.
Lastly, (3q + 2) 2 = 9q 2 + 12q + 4 = (9q2 + 12q + 3) + 1 = 3(3q2 + 4q + 1) + 1
which can be written in the form 3m + 1, since 9q 2 + 12q + 3, i.e., 3(3q 2 + 4q + 1) is divisible by 3.
Therefore, the square of any positive integer is either of the form 3m or 3m + 1 for some integer m.
Express each number as product of its prime factors :
(i) 140
(ii) 156(iii) 3825
(iv) 5005
(v) 7429
(i) 140
(ii) 156
140
156
70
2
35
2
5
78
2
39
2
7
So, 140 = 2 × 2 × 5 × 7 = 2 2 × 5 × 7
3
13
So, 156 = 2 × 2 × 3 × 13 = 2 2 × 3 × 13
(Rest Try your self)
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Page # 94
Ex.7
Sol.
Find the LCM and HCF of the following pairs of integers and verify that LCM × HCF = product of two
numbers.
(i)
26 and 91
(ii) 510 and 92
(iii) 336 and 54
(i)
26 and 91
26
13
2
So, 26 = 2 × 13
91
13
7
So, 91 = 7 × 13
Therefore, LCM (26, 91) = 2 × 7 × 13 = 182
HCF (26, 91) = 13
Verification LCM × HCF = 182 × 13 = 2366 and 26 × 91 = 2366
i.e.,
LCM × HCF = product of two numbers.
Ex.8
Sol.
(Rest Try your self)
Find the LCM and HCF of the following integers by applying the prime factorisation method.
(i)
12, 15 and 21 (ii) 17, 23 and 29
(iii) 8, 9 and 25
(i)
12, 15 and 21
12
6
2
So,
2
3
12 = 2 × 2 × 3 = 22 × 3
15
5
3
So,
15 = 3 × 5
21
3
7
So,
21 = 3 × 7
Therefore, HCF (12, 15, 21) = 3 ; LCM = (12, 15, 21) = 2 2 × 3 × 5 × 7 = 420
(Rest Try your self)
Ex.9
Given that HCF (306, 657) = 9, find LCM (306, 657).
Sol.
306×657
306×657
LCM (306, 657) = HCF (306, 657) =
= 22338.
9
Ex.10 Prove that square of any odd integer is of the form 8k + 1, k an integer.
Sol.
For any odd integer is of the form 2m + 1 and (2m + 1)2 = 4m2 + 4m + 1
= 4 m (m + 1) + 1
Now, m (m + 1) is alwyas even, say 2k, hence 4m(m + 1) = 4 × 2k
(2m + 1)2 = 8k + 1
Ex.11 Check whether 6n can end with the digit 0 for any natural number n.
Sol.
If the number 6 n, for any natural number n, ends with digit 0, then it would be divisible by 5. That is,
the prime factorisation of 6 n would contain the prime number 5. This is not possible because
6 n = (2 × 3)n = 2n × 3n ; so the only primes in the factorisation of 6n are 2 and 3 and the uniqueness
of the Fundamental Theorem of Arithmetic guarantees that there are no other primes in the factorisation
of 6n. So, there is no natural number n for which 6n ends with the digit zero.
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Page # 95
Ex.12 Explain why 7 × 11 × 13 + 13 and 7 × 6 × 5 × 4 × 3 × 2 × 1 + 5 are composite numbers.
Sol.
(i)
7 × 11 × 13 + 13
= (7 × 11 + 1) × 13
= (77 + 1) × 13
= 78 × 13
= (2 × 3 × 13) × 13
[ 78 = 2 × 3 × 13]
= 2 × 3 × 13 2
Since, 7 × 11 × 13 + 13 can be expressed as a product of primes, therefore, it is a composite number.
(Rest Try your self)
Ex.13 Prove that
Sol.
5 is irrational.
Let us assume, to the contrary, that
5 is rational.
So, we can find coprime integers a and b ( 0) such that
a
5 =
b
5b= a
Squaring on both sides, we get
5b 2 = a2
Therefore, 5 divides a2.
Therefore, 5, divides a
So, we can write a = 5c for some integer c.
Substituting for a, we get
5b 2 = 25c 2
b 2 = 5c 2
This means that 5 divides b 2, and so 5 divides b.
Therefore, a and b have at least 5 as a common factor.
But this contradicts the fact that a and b have no common factor other than 1.
This contradiction arose because of our incorrect assumption that 5 is rational.
So, we conclude that
5 is irrational.
Ex.14 There is a circular path around a sports field. Sonia takes 18 minutes to drive one round of the field,
while Ravi takes 12 minutes for the same. Suppose they both start at the same point and at the same
time, and go in the same direction. After how many minutes will they meet again at the starting point?
Sol.
[Hint : Take LCM of 18 and 12]
Ex.15 Prove that 3 + 2 5 is irrational.
Sol.
Let us assume, to the contrary, that 3 + 2 5 is rational.
That is, we can find coprime integers a and b (b
Therefore,
0) such that 3 + 2 5 =
a
b
a
– 3=2 5
b
a–3b
=2 5
b
a–3b
= 5
2b
a 3
– =
2b 2
5
Since a and b are integers, we get
But this contradicts the fact that
a
3
a – 3b
– is rational, and so
2b 2
2b
5 is rational.
5 is irrational. This contradiction has arisen because of our
incorrect assumption that 3 + 2 5 is rational.
So, we conclude that 3 + 2 5 is irrational.
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Page # 96
Ex.16 Show that 5 – 3 is irrational.
Sol.
Suppose 5 – 3 is a rational number (say p)
Then 5 –
5–p=
3 =p
3
Since p is a rational number and 5 is a rational
5 – p being the difference of two rational numbers is a rational number because the set of rational
numbers are closed w.r.t. the operation of subtraction.
3 is a rational number But, it is an irrational number
Our supposition is wrong. Hence 5 –
3 irrational .
Ex.17 Prove that the following are irrationals :
(i)
Sol.
1
(ii) 7 5
2
(iii) 6
2
(Try yourself)
Ex.18 Without actually performing the long division, state whether the following rational numbers will have a
terminating decimal expansion or a non-terminating repeating decimal expansion.
(i)
13
3125
23
(vi) 23 52
Sol.
(i)
(ii)
17
8
129
(vii) 22 57 75
(iii)
64
455
(iv)
15
1600
(v)
29
343
6
15
(ix)
35
50
(x)
77
210
(viii)
13
13
= 5
3 1 25
5
Hence, q = 5 5, which is of the form 2n 5 m (n = 0, m = 5). So, the rational number
13
has a
3 1 25
terminating decimal expansion.
(ii)
17
17
= 3
8
2
Hence, q = 2 3, which is of the form 2n 5m (n = 3, m = 0). So, the rational number
17
has a terminating
8
decimal expansion.
(iii)
64
64
=
5 7 13
455
Hence, q = 5 × 7 × 13, which is not of the form 2 n 5 m. So, the rational number
non-terminating repeating decimal expansion.
64
has a
455
(Rest Try your self)
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Page # 97
Ex.19 Write down the decimal expansions of those rational numbers in Question 1 above which have terminating
decimal expansions.
Sol.
(i)
13
3 1 25
=
(ii)
13 13×2 5
416
= 0.00416
=
=
55 55 ×25
10 5
17
8
=
17
23
17×53 17×5 3
2125
=
=
= 2.125
2 3 ×5 3
10 3
103
(Rest Try your self)
Ex.20 The following real numbers have decimal expansions as given below. In each case, decide whether
p
they are rational, or not. If they are rational, and of the form
, what can you say about the prime
q
factors of q?
Sol.
(i)
43.123456789
(ii)
0.120 1200 12000 120000....
(iii)
43.123456789
(i)
43.123456789
Since, the decimal expansion terminates, so the given real number is rational and therefore of the form
p
. 43.123456789
q
=
43123456789
1000000000
=
43123456789
109
=
43123456789
(2×5)9
=
43123456789
29 59
Hence, q = 2 9 59
The prime factorization of q is of the form 2n 5m, where n = 9, m = 9.
(ii)
0.120 1200 12000 120000....
Since, the decimal expansion is neither terminating nor non-terminating repeating, therefore, the
given real number is not rational.
(Rest Try your self)
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Page # 98
EXERCISE – I
Q.1
Prove that
2 is not a rational number or
there is no rational whose square is 2.
3
UNSOLVED PROBLEMS
Q.14
State fundamental theorem of Arithmetic.
Q.15
For any two positive integers, state the relation
between the numbers, their H.C.F. and L.C.M.
Q.2
Prove that
3 is irrational.
Q.3
Prove that 2 + 3 is irrational.
Is this result true for three positive integers?
Q.16
Explain why 7 × 11 × 13 + 13 is a composite
number
Q.4
Prove that
2 + 3 is irrational.
Q.17
Q.5
Use Euclid's division lemma to show that the
If
p
is a rational number (q
q
conditi on
square of any positive integer is either of the
on q
representation of
form 3m or 3m +1 for some interger m.
Q.6
Show that one and only one out of n, n + 2 or
so
0), what is the
t ha t t he
decimal
p
is terminating?
q
Q.18
Write a rational number between
2 and
3.
Q.19
Complete the missing entries in the following
n + 4 is divisible by 3, where n is any positive
integer.
factor tree?
Q.7
Use Euclid's algorithm to find the HCF of 4052
2
and 12576.
3
Box 2
Q.8
Find the HCF of 1848, 3058 and 1331.
Q.9
Using Euclid's division, find the HCF of 56, 96
and 404
Q.10
7
Box 1
Q.20
Find the prime factors of 560.
Q.21
Find the missing numbers in the following
factorisation :
Find the L.C.M and H.C.F. of 1296 and 2520
(box 4)
by applying the fundamental theorem of
(box 3)
2
arithmeti c me thod i.e. using t he pri me
factorisation method.
(box 2)
2
(box 1)
3
Q.11
Given that H.C.F. (336, 54) = 6. Find L.C.M.
5
5
(336, 54)
Q.22
Q.12
Given that L.C.M. (150, 100) = 300, find H.C.F.
Find the H.C.F. and L.C.M. of 17, 23, 37 by
applying prime factorisation method.
(150, 100).
Q.23
Q.13
State Euclid's division lemma.
Given that H.C.F. (14, 35) = 7, find L.C.M.
(14, 35).
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Q.24
Page # 99
Without performing long division, state
Q.31
Examine whether the following numbers are
rational or irrational :
84
whether the number
455
will have a
(i) 2
terminating or a non-terminating but repeating
3
2
(ii)
2
(iv)
2 3
3
3
2
decimal representation.
Q.25
(iii) 3
Write down the decimal representation of
3 3
3
77
.
210
Q.32
Q.26
The following real numbers have decimal
Show that p 2 – 1 is divisible by 8, where p is
an odd positive interger.
expansion as given below. In each case
decide whether it is rational or not. If rational,
Q.33
Prove that
5 is an irrational number..
Q.34
Use Euclid's division lemma to show that the
what can be said about the prime factors of
denominator.
cube of any positive integer is of the form 9m,
(i)
4.59
9m + 1 or 9m + 8.
(ii)
0.13013001300013000013……
Q.35
Check whether 7n can end with digit 0, for any
natural number n.
(iii)
0.0 6012
Q.36
Q.27
If H.C.F. (65, 117) is expressed in the form
65m + 117n, then find the value of m.
Find two irrational numbers between 0.1 and
0.12.
Q.28
Find a rational number and also an irrational
Find the g.c.d. of the following pairs of polynomials
number between the numbers.
a = 0.101001000100001……,
Q.37
(x + 1)2 (x + 7)
b = 0.1001000100001……
Q.29
Show that any positive odd integer is of the
form 4q + 1 or 4q + 3, where q
Q.30
4(x – 3) 2 (x – 1) (x + 1) 3 and 6(x – 1) 2
Q.38
(x – 2)2 (x + 3) (x – 4) and (x – 2) (x + 2) (x –
5)
Z+ .
Without actually performing the long division,
Q.39
(2x – 7) (3x + 4) and (2x – 7)2 (x + 3)
17
will
1600
Q.40
(3x – 2)2 (2x + 3)3 (x – 1) and (3x – 2)3 (2x +
state whether the rational number
3) (x – 1)3
have terminating or non-terminating but
repeated decimal representation.
Q.41
(x – 1) (x + 1)3 and (x – 1)3 (x + 1)
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Q.42
(x + 4)2 (x – 3)3 and (x – 1) (x + 4) (x – 3)2
Q.64
(6x4 – 13x3 + 6x2) and (8x4 – 36x3 + 54x2 – 27x)
Q.43
24(x – 3) (x – 2)2 and 15(x – 2) (x – 3)3
Q.65
(x3 – x2 – x – 2) and (x3 + 3x2 – 6x – 8)
Q.44
16 – 4x2 and x2 + x – 6
Q.66
(4x5 + 16x4 – 44x2 – 24x) and (2x5 – 6x3 + 2x)
Q.45
xy – y and x4 y – xy
Q.67
(3x3 – 14x2 + 9x + 10) and (15x3 – 34x2 + 21x – 10)
Q.46
2x2 – 7x + 3 and 3x2 – 7x – 6
Q.68
4x2(x2 – a2 ) and 9x2(x3 – a3 )
Q.47
x3 + 64 and x2 – 16
Q.69
2(a2 – b2) and 3(a 3 – b 3)
Q.48
x3 + 2x2 – 3x and 2x3 + 5x2 – 3x
Q.70
(x2 + 3x – 4) and (x3 – 2x2 – 2x + 3)
Q.49
22x(x + 1)2 and 36x2 (2x2 + 3x + 1)
Q.71
12(x4 – 25) and 8(x4 + 4x2 – 5)
Q.50
3 + 13x – 30x2 and 25x2 – 30x + 9
Q.72
Find the values of a and b so that the polynomial
Q.51
(x3 – y3 ) and (x4 + x2y2 + y4)
Q.52
2x2 + 7xy + 3y2 and 2x2 + 6xy + x + 3y
Q.53
56(x6 y2 – x2y6) and 72(x5 y3 + 3y5 x3 + 2y7 x)
Q.54
54(x3 + 8y3 ) and 90(x3 + 7x2 y + 16xy2 + 12y3)
Q.55
(4x4 + y4) and (2x3 – xy2 – y3 )
Q.56
x3 – y3; x3 y – y4 and y2(x – y)2 (x2 + xy + y2)
(i) 12(x3 + x2 + x + 1) and 18(x4 – 1).
Q.57
(2x2 – 3xy)2 ; (4x – 6y)3 and (8x3 – 27y3 )
(ii) 12(3x4 – 14x3 – 5x2) and 30(3x5 + 4x4 + x3)
Q.58
(4x4 + y4); (2x3 – xy2 – y3) and (2x2 + 2xy + y2)
Q.59
x4 – x3 + x – 1 and x4 + x2 + 1
(i) x3 + 2x2 – 3x and 2x3 + 5x2 – 3x
Q.60
(8x6 – 32x5 + 128x3 – 128x2 ) and (12x6 – 36x5 +
(ii) 4(x4 – 1) and 6(x3 – x2 – x + 1)
x3 + ax2 + bx – 42 is divisible by x2 – x – 6.
Q.73
48x3 )
+ ax2 + bx – 6 is completely divisible by x2 – 4x – 3.
Q.74
(x3 – x2 – x + 1) and (x4 – 2x3 + 2x – 1)
Q.62
2x y(x – y ) and 35 xy (x – y)
Q.63
(x2 + 4x – 21) and (x3 + 7x2 – 9x – 63)
Find the values of a and b so that the polynomial
f(x) = 3x3 + ax2 – 13x + b is divisible by x2 – 2x – 3.
Q.75
Q.76
Q.77
Q.61
Find the values of a and b so that the polynomial x3
Find the GCD of the polynomials
Find the GCD of the polynomials :
If x2 – x – 6 is the GCD of the expressions (x + 2)
(2x2 + ax + 3) and (x – 3) (3x2 + bx + 8).
Find the values of a and b.
2
2
2
2
Q.78
Find the GCD of the polynomials :
2(x4 – y4 ), 3(x2 + 2x2 y – xy2 – 2y3 ).
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Q.79
Page # 101
If (x2 – x – 2) is the GCD of the expressions
Q.80
Q.88
Find the values of a and b such that the
(x – 2) (2x + ax + 1) and (x + 1) (3x + bx + 2),
polynomials. P(x) and Q(x) have (x + 3)
find the values of a and b.
(x – 2) as their HCF :
Find the GCD of the polynomials :
P(x) = (x2 – 4x – 21) (x2 – 4x + a)
(i) p(x) = 45(2x4 – x3 – x2) and q(x) = 75(8x5 + x2).
Q(x) = (x2 – 5x + 6) (x2 – 4x + b)
2
2
Q.89
(ii) p(x) = 36(3x4 + 5x3 – 2x2) and q(x) = 54(27x4 – x).
If (x
) is the GCD of ax2 + bx + c and
bx2 + cx + a, prove that either
a = 0 or a3 + b3 + c 3 = 3abc.
(iii) p(x) = 42(2x3 – 5x2 – 3x) and q(x) = 60(8x4 + x).
Q.90
If (x
) is the GCD of ax2 + bx + c and
cx2 + bx + a, prove that
Q.81
(x + 1) (x – 4) is the g.c.d. of the polynomials
a + b + c = 0 or a – b + c = 0
(x – 4) (2x2 + x – a) and (x + 1) (2x2 + bx – 12).
Find a and b.
Q.91
Q.82
Q.83
(x – 3) is the g.c.d. of x3 – 2x2 + px + 1 and
3x2 – 2mx – 4 have a common linear factor,
x2 – 5x + q. Find the 6p + 5q.
find the values of m.
For what value of k, the g.c.d. of x2 + x –
Q.92
(2k + 2) and 2x2 + kx – 12 is x + 4 ?
Q.84
If t he po lyno mials x 2 – 4m x + 2 and
If G.C.D. of (x – 5) (x2 – x – a) and (x – 4)
If (x
) is the HCF of px2 + qx + c and ax2 + bx
+ c, prove that
Q.93
(p
a) = (b – q).
Find the HCF (GCD) of the polynomials :
(x2 – 2x – b) is (x – 4) (x – 5), find the values
(i) (x – 3) (x + 5)2, (x + 5) (x + 7)2 and (x + 2)
of a, b.
(x + 5)3
Q.85
Find the values of k for which the g.c.d. of
(ii) 2(x – 7) (x + 7) 2, 4(x – 7)2 (x + 8) and
x2 – 2x – 24 and x2 – kx – 6 is x – 6.
8(x2 – 49)
Q.86
Find the H.C.F. of x – 1 and x + x + x + 1.
4
3
2
(iii) x2 – 1, x4 – 1 and (x – 1)2
Q.87
Find the va lue of a and b s o that t he
(iv) 4(x + 2), 8(x + 3) and 16(x + 4)
polynomials P(x) and Q(x) have (x + 1)
(x – 2) as their HCF :
(v) 3(x + 3), 5(x + 3) (x + 5) and 7(x + 4)
P(x) = (x2 + 3x + 2) (x2 + x + a)
Q.94
Q(x) = (x2 – 3x + 2) (x2 – 3x + b)
Fine what value(s) of k is the HCF of x2 + x –
(2k + 2) and 2x2 + kx – 12, (x + 4) ?
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Q.95
If the HCF of the polynomials
37. 2(x – 1) (x + 1)2
f(x) = (x – 1) (x2 + 3x + a) and,
39. (2x – 7)
g(x) = (x + 2) (x2 + 2x + b) is (x – 1) (x + 2)
find a and b.
Q.96
38. (x – 2)
40. (3x – 2)2 (2x + 3) (x – 1)
41. (x – 1) (x + 1)
42. (x + 4) (x – 3)2
43. 3(x – 3) (x – 2)
44. (x – 2)
45. (x – 1)y
46. (x – 3)
47. (x + 4)
48. x(x + 3)
49. 2x(x + 1) 50. (5x – 3)
Find a and b so that the polynomials
f(x) = (x2 + 3x + 2) (x2 + 2x + a)
and
g(x) = (x + 7x + 12) (x + 7x + b) may
2
51. x2 + xy + y2
52. x + 3y
53. 8xy2(x2 + y2)
54. 18(x + 2y)
2
have (x + 1) (x + 3) as their HCF.
Q.97
If (x – 2) is a factor of x 2 + ax + b and
55. 2x2 + 2xy + y2
56. x3 – y3
57. 2x – 3y
58. 2x2 + 2xy + y2
59. x2 – x + 1 60. 4x2(x – 2)
61. (x – 1)2 (x + 1)
62. xy(x – y)
63. (x + 7) (x – 3)2
64. x(2x – 3) 65. (x – 2)
66. 2x(x2 – x – 1)
67. (3x – 5)
68. x2 (x – a)
69. (a – b)
70. (x – 1)
71. 4(x2 + 5)
a + b = 1, find the values of a and b.
2
Q.98
If (x + 3) (x – 2) is the GCD of f(x) = (x + 3) (2 x
– 3x + a) and, g(x) = (x – 2) (3x2 + 10x – b)
find the values of a and b.
ANSWER KEY
7. HCF = 4
8. HCF = 11
9. HCF = 4
72. a = 6, b =
13
10. HCF = 72, LCM = 45360 11. LCM = 3024
74. a =
12. HCF = 50
75. (i) 6(x + 1) (x2 + 1)
15. HCF × LCM = a × b, No
16. More than 2 factors
6, b = 11
6
(ii) 6x2(3x + 1)
76. (i) x(x + 3) (ii) 2(x2 – 1)
17. Factors of q are in the form of 2m or 5n or 2m × 5n
18. 1.5
4, b =
73. a =
77. a =
7, b = 10
78. x2 – y2
79. a = 3, b =
80. (i) 15x2(2x + 1) (ii) 18x (3x – 1) (iii) 6x(2x + 1)
4
20. 2 × 5 × 7
21. 25, 75, 150, 300
22. 1,14467
24. Non-terminating
23. 70
81. a = 1, b =
5
84. a = 12, b = 15
25. 0.3 6
26. (i) Rational (ii) Not Rational (iii) Rational
27. 0.101001000...., 0.1121231234....
87. a =
91. m = ±
28. 0.1002, 0.100212112111....
6, b =
82. 10
83. k = 5
85. k = 5
86. (x + 1) (x2 + 1)
4 88. a = 4, b =
21
1
2
93. (i) x + 5 (ii) 2(x – 7) (iii) x – 1 (iv) 4 (v) 1
30. Terminating
31. (i) Irrational
(iii) Rational
35. Not
7
19. 21, 42
(ii) Irrational
(iv) Irrational
36. m = 2, n = –1
94. 5
95. a = 2, b =
96. a =
3, b = 6
98. a =
2, b = 3.
97. a =
3
3, b = 6
Corporate Head Office : Motion Education Pvt. Ltd., 394 - Rajeev Gandhi Nagar, Kota-5 (Raj.)
REAL NUMBERS
Page # 103
EXERCISE – II
BOARD PROBLEMS
Questions Carrying 1 Mark
Q.1
p
If
is a rational number (q
q
Q.14
Prove that
2 is an irrational number..
[Delhi-2009/AI-2008]
Q.15
Prove that
5 is an irrational number..
0), what is
[Delhi-2009/AI-2008]
condition of q so that the decimal representation
of
p
is terminating?
q
[Delhi-2008]
Q.16
Prove that 3 + 2 is an irrational number..
[AI-2009]
Q.2
Write a rational number between
2 and 3 .
[AI-2008]
Q.17
Q.3
Complete the missing entries in the following
factor tree :
[Foreign-2008]
Prove that 3 + 5 2 is an irrational number..
[AI-2009]
Q.18
Show that the square of any positive odd
integers is of the form 8m + 1, for some integer
m.
[Foreign-2009]
Q.19
Prove that 7 + 3 2 is not a rational number..
[Foreign-2009]
2
3
7
Q.4
The decimal expansion of the rational number
43
, will terminate after how many places
2 4 ·5 3
of decimals?
[Delhi-2009]
Q.5
Find the [HCF × LCM] for the numbers 100
and 190.
[AI-2009]
Q.6
Find the [HCF × LCM] for the numbers 105
and 120.
[AI-2009]
Q.7
Write whether the rational number
ANSWER KEY
1.
q = 2 n × 5 m, where n and m are whole
numbers.
2.
51
will
1 50 0
2 = 1.41.......,
One rational no. between
have a terminating decimal expansion or a nonterminating repeating decimal expansion.
[Foreign-2009]
Q.8
The HCF and LCM of two numbers are 9 and
360 respectively. If one number is 45, write
the other number.
[Foreign-2009]
3 = 1.73.....
2 and
3 is 1.5.
2
3.
3
42
21
7
Questions Carrying 3 Marks
43
43
=
= 0.0215
2 4 ·5 3
2 0 00
Q.9
Show that 5 – 2 3 is an irrational number..
[Delhi-2008]
4.
After 4 decimal;
Q.10
Show that 2 –
5.
HCF × LCM = 100 × 190 = 19000
6.
HCF × LCM = 105 × 120 = 12600
7.
51
1 5 00
3 is an irrational number..
[Delhi-2008]
Q.11
Show that 5 + 3 2 is an irrational number..
[Delhi-2008]
Q.12
Prove that
3 is an irrational number..
[Delhi -2009/AI-2008]
Q.13
Use Euclid's Division Lemma to show that the
square of any positive integer is either of the
form 3m or 3m + 1 for some integer m.
[Foreign-2008/AI-2008]
17
; 500 = 22 × 53 (2m · 5 n). So, it
5 00
has terminating expansion.
8.
Other number =
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9
3 60
45
72
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REAL NUMBERS
Page # 104
EXERCISE – III
Q.1
A rational number between
MULTIPLE CHOICE QUESTIONS
1
1
and
is
4
3
7
(B) 0.29
24
13
(C)
(D) all the above
48
An irrational number is
(A) a terminating and nonrepeating decimal
Q.10
(A)
Q.2
Q.11
(B) a nonterminating and non repeating decimal
(C) a terminating and repeating decimal
Q.3
(D) a nonterminating and repeating decimal
Which of the following statements is true
(A) Every point on the number line represents
a rational number
(B) Irrational numbers cannot be represented
by points on the number line
Q.12
22
is a rational number
7
(D) None of these
The set of real numbers does not satisfy the
property of
(A) multiplicative inverse
Q.13
(C)
Q.4
Q.5
(B) additive inverse
(C) multiplicative identity
(D) none of these
If m is an integer, then square of any positive
integer is of the form :
(A) 2m + 1
(C) 3m or 3m + 1
Q.6
Q.7
Q.8
Q.9
(B) 2 m or 3m
(D) 2m + 1 or 3m + 1
If 'm' is an irrational number then '2m' is
(A) a rational number
(B) an irrational number
(C) a whole number
(D) a natural number
The value of 3 is
(A) 0.414
(B) 2.256
(C) 1.732
(D) none
The sum of a rational and an irrational number.
(A) an irrational number
(B) a rational number
(C) an integer
(D) a whole number
The product of two irrationals is
(A) a rational number
(B) an irrational number
(C) either A or B
(D) neither A nor B
Q.14
Q.15
The value of 1.34
4.12 is
133
371
(A)
(B)
99
90
5169
5411
(C)
(D)
990
990
Which of the following statements is false?
(A) Every fraction is a rational number
(B) Every rational number is a fraction
(C) Every integer is a rational number
(D) All the above
An irrational number is :
(A) a terminating and non-repeating decimal
(B) a non-terminating and non-repeating
decimal
(C) a terminating and repeating decimal
(D) a non-terminating and repeating decimal
7 × 11 × 13 + 13 and 7 × 6 × 5 × 4 × 3 ×
2 × 1 + 5 are
(A) composite numbers
(B) whole number
(C) prime numbers
(D) none of these
HCF of two numbers is 113, their LCM is 56952.
If one number is 904, the other number is :
(A) 7719
(B) 7119
(C) 7791
(D) 7911
For what least value of n (where n is a natural
number), (24)n is divisible by 8?
Q.16
(A) 0
(B) –1
(C) 1
(D) no value of x possible
is
(A) a rational
(B) an irrational
(C) both (A) and (B)
(D) sometimes rational, sometimes irrational
Q.17
Expressing 0.358 as a rational number, we get :
358
358
(B)
100
999
355
(C)
(D) None of these
990
Which of the following numbers has the
terminating decimal representation ?
(A)
Q.18
(A)
1
7
(B)
1
3
(C)
3
5
(D)
17
6
Corporate Head Office : Motion Education Pvt. Ltd., 394 - Rajeev Gandhi Nagar, Kota-5 (Raj.)
REAL NUMBERS
Q.19
Page # 105
Missing numbers in the following factor tree
are :
x
y
2
2
(A) x = 34, y = 68
Q.20
Q.28
Express 0.75 as rational number..
(A)
75
90
(B)
25
33
(C)
3
4
(D) None
y
(B) y = 34, x = 68
(C) y = 34, x = 34
(D) y = 68, x = 68
A lemma is an axiom used for proving :
Q.29
(A) other statement
(B) no statement
Express 0. 358 as rational number
(A)
358
1000
(B)
358
999
(C)
355
990
(D) All
(C) contradictory statement
(D) none of these
Q.21
1
,b
3 2 2
If a
1
, then the value of
3 2 2
a 2 + b2 is :
(A)
34
(C)
36
Q.22
(C)
a
b
a
is
b
(B)
b
a
b
a
1
0
Q.32
(B) 0
(C) does not exist
If
Q.31
a
b
(D)
Multiplicative inverse of '0' is
(A)
Q.25
(B) multiplication
(D) none of these
The additive inverse of
(A)
Q.24
(B) 35
(D) 37
5 = 2.236 and
(D) none of these
3 = 1.732, then the value
2
7
is
5
3
5
3
(A) 14
(B) 14.39
(C) 14.392
(D) 16
A rational number can be expressed as a
terminating decimal if the denominator has
factors
(A) 2 or 5
(B) 2, 3 or 5
(C) 3 or 5
(D) none of these
Express 0.75 as rational number.
Q.33
of
Q.26
Q.27
Which of the following statements is true?
(A)
5
7
(B)
11
13
(C)
5
7
(D)
5
7
The set of all irrational number is closed for
(A) addition
(C) division
Q.23
Q.30
(A)
(C)
75
99
(B)
75
90
3
4
(D) None
7
9
9
11
11
13
7
9
5
7
11
13
7
9
9
11
9
11
11
13
7
9
9
11
______ is a series of well defined steps, which
gives a procedure for solving a type of problem.
(A) Theorem
(B) Statment
(C) Algorithm
(D) None of these
Euclid's division algorithm can be applied to :
(A) only positive integers
(B) only negative integers
(C) all integers
(D) none of these
Expressing 0.625 as a rational number, we get :
(A)
62 .5
1000
(B)
5
8
(C)
625
100
(D) None of these
Q.34
A rational number in its standard from can be
expressed as a terminating decimal, if the
denominator has factors :
(A) 2 or 5
(B) 2, 3 or 5
(C) 3 or 5
(D) None of these
Q.35
0 .36 as a fraction in the simplest form is :
(A)
36
90
(B)
36
100
(C)
11
30
(D)
33
90
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REAL NUMBERS
Page # 106
Q.36
0.254 as a fraction in the simplest form is
14
(A)
55
(C)
Q.37
Q.38
42
165
Q.40
Q.41
Representation of 3 .6 as a fraction in the
simplest form is :
(A)
11
13
(B)
11
3
(C)
36
10
(D)
3
11
5
6 is :
(A)
16
1000
(B)
16
99
(C)
16
100
(D)
8
50
0.1010010001 …… is :
(A) a rational number
(B) a repeating decimal number
(C) an irrational number
(D) both (A) and (C)
5
The value of 4 –
is
1
(A)
40
31
(B)
4
9
(C)
1
8
(D)
31
40
(A)
3
2
(B)
3
2
(C)
1
2
(D)
1
2
If
6 = 2.449 then the value of
to
(A) 1.225
(C) 0.613
(B) 0.816
(D) 2.449
IV.
17
8
(A)
2
(B)
4
(C)
9
(D)
16
Q.48
The quotient of (3 2 3 ) (3 2 3) is :
Q.49
(A) a rational
(B) an irrational
(C) both (A) and (B)
(D) either (A) or (B)
Which of the following is a rational number
Q.51
Q.52
3 2
is close
2 3
2
1
1
Set of natural numbers is a subset of
(A) set of even numbers
(B) set of odd numbers
(C) set of composite numbers
(D) set of real numbers
Q.50
The sum of t he a ddi ti ve i nver se a nd
multiplicative inverse of 2 is
1
2
3
3
II.
(A) I
(B) IV
(C) II
(D) III
Which of the following is not a rational number?
(A)
1
4
1 .728
is
5 5 5 5
Q.47
1
2
3
III.
Q.46
3
Q.43
Q.45
(A) 0
(B) 5
(C) can't be determined
(D) none
The greatest among the following is
I.
0.16 as rational number in the simplest form is :
1
Q.42
The value of
126
495
(D)
(A) a rational number
(B) an irrational number
(C) can't say
(D) both (A) and (B)
Q.39
Q.44
254
(B)
1000
5
(B)
6
(C) 8
(D) 9
The sum of two rational number is always
(A) an irrational number
(B) a rational number
(C) a fraction
(D) none of these
The product of a rational and an irrational
number is always :
(A) a irrational number
(B) a rational number
(C) a fraction
(D) none of these
The sum of a rational number and an irrational
number is always :
(A) an irrational number
(B) a rational number
(C) an integer
(D) a whole number
Corporate Head Office : Motion Education Pvt. Ltd., 394 - Rajeev Gandhi Nagar, Kota-5 (Raj.)
REAL NUMBERS
Q.53
Page # 107
The product of two irrational number is :
Q.61
In a morning walk three persons step off together.
Their steps measures 80 cm, 85 cm and 90 cm
respectively. The minimum distance each should
walk so that they can cover the distance in
complete step is.
(A) 122 m 40 cm
(B) 132 m 60 cm
(C) 125 m 31 cm
(D) 120 m 40 cm
Q.62
The number
(A) a rational number
(B) an irrational number
(C) either (A) or (B)
(D) neither (A) nor (B)
Q.54
1
is :
2
(A) a rational
(C) both (A) and (B)
(D) none of these
If q is some integer, then any positive odd
Q.63
integer is of the form :
(A) q – 1
(B) 2q
(C) 4q + 1 or 4q – 1
Q.64
(D) 4q + 1 or 4q + 3
Q.56
If p : All integers are rational number and q :
Every rational is an integer, then which of the
following statements is correct?
1
(iii) x > y
(D) All (i), (ii), (iii) are correct
Q.67
(A) A is false and R is the correct explanation of A
(B) A is true and R is the correct explanation of A
(C) A is true and R is false
Q.68
(D) both A and R are true
8) , then the value of
Q.60
The numbre 6
(A) rational
(C) can't say
(B) 25
(D) 34
2 6
x2
1
x2
(D) none of these
3
Q.69
2
(B)
2
3 is
3
2
(A)
2
(B)
3
(C)
5
(D)
11
The number 3
3
(A) rational
(C) both
is :
2 and
(C) 1.5
(D) 1.8
The irrational number between 2 and 3 is
3 is
3
(B) irrational
(D) can't say
The rational number between
(A)
2
5
(B)
1
5
(C)
3
5
(D)
4
5
2 is
(B) irrational
(D) none
1
1
(B) 34, 36
1
2
(C) only (ii) is correct
(A) 24
(C) 30
1
Rational number between
(A)
If A : Every whole number is a natural number
and R : 0 is not a natural number, then which
of the following statement is true?
y ,
x
Q.66
(B) only (ii) and (iii) are correct
If x = (3
y
Two tankers contain 850 litres and 680 litres
of petrol respectively. The maximum capacity
of a container which can measure the petrol
of either tanker in exact number of times is :
(A) 160 litres
(B) 168 litres
(C) 170 litres
(D) 180 litres
For any two rational number x and y, which of
the following properties are correct?
(A) only (i) and (ii) are correct
Q.59
is
Q.65
(D) both p and q are false
Q.58
2
where x, y > 0 is
(A) rational
(B) irational
(C) both
(D) none
Two irrational numbers between
2 and 3 are :
1
(C) both p and q are true
(ii) x = y
x
(C) 68, 34
(B) p is true and q is false
(i) x < y
The number
(A) 22, 64
(A) p is false and q is true
Q.57
3
(A) rational number
(B) irrational number
(C) can't say
(D) none
(B) an irrational
Q.55
2
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1
1
and
is
2
3
: [email protected]
REAL NUMBERS
Page # 108
3
3
Q.70
2
2
3
3
2
2
(A) 15
(C) 10
Q.71
(B) 16
(D) 24
1008 is equal to :
4
63
Q.81
(A) 1
(C) 4
Q.72
Q.80
is equal to :
7
(B) 2
(D) 6
5 is :
Q.74
Q.75
Q.76
Q.77
88
5
(C)
44
25
(D) none
If p : Every fraction is a rational number and
Which of the following is a rational number(s) ?
(A)
(C)
Q.83
2
9
3
17
(B)
4
7
(D) All the three
3
is a ____ .
0
(A) positive rational number
121
is
23 32 75
(B) negative rational number
(C) either positive or negative rational number
(A) a terminating decimal number
(B) a non-terminating repeating decimal
(C) a rational number
(D) both (B) and (C)
The largest number of four digits exactly
divisible by 12, 15, 18 and 27 is :
(A) 9720
(B) 9820
(C) 9920
(D) 9930
(D) neither positive nor negative rational
number
If x, y, z be rational number such that x > y
and z < y then .......
1
3
1
8
8
1
7
7
1
6
6
4
9
(C) 17
(A) z > x
(C) y < z
Q.85
1
is
5 2
5
1 1
a b
(B)
25
36
(D)
31
17
a
is equal to :
The domain of the function
ƒ(x) = x 4
(A) R – {4}
(C) [5, )
Q.84
(B) 1
(D) 5
If a = 2 and b = 3, then
(A)
Q.79
(B)
(D) Both p and q are false
Q.82
(A) a rational
(B) an irrational
(C) an integer
(D) not real
The greatest number of 6 digits exactly divisible
by 24, 15 and 36 is :
(A) 999998
(B) 999999
(C) 999720
(D) 999724
(A) 0
(C) 2
Q.78
53
3
(B) p is false and q is true
(C) Both p and q are true
2) is :
(6
(A)
q : Every rational number is a fraction, then
which of the following is correct?
(A) p is true and q is false
(A) an irrational
(B) a rational
(C) neither (A) nor (B)
(D) all of the above
Q.73
The equivalent rational form of 17 .6 is
x 5 + |x| + x2
(B) R – {4, 5}
(D) R
Q.86
Q.87
(B) z < x
(D) y > x
If A : The quotient of two integers is always a
1
rational number and R : is not rational, then
0
which of the following statement is true
(A) A is true and R is the correct explanation of A
(B) A is false and R is the correct explanation of A
(C) A is true and R is false
(D) Both A and R are false
For what least value of n, where n is a natural
number, 5n is divisible by 3?
(A) 1
(B) 0
(C) 2
(D) no value of n is possible
Which one is the correct alternative of the
decimal representation of an irrational number ?
(A) non - terminating, non-repeating
(B) terminating
(C) termiating, repeating
(D) non-terminating, repeating
Corporate Head Office : Motion Education Pvt. Ltd., 394 - Rajeev Gandhi Nagar, Kota-5 (Raj.)
REAL NUMBERS
Q.88
(C)
Q.90
133
990
(B)
5169
990
(D)
371
290
(A)
5411
990
1
3
3
1
3
3
(A) 6765207
(B) 6765201
(D) 23.10100100010000.....
(C) 6765206
(D) 6765209
Two candles are of different lengths and
thicknesses. The short and the long ones
can burns respectively for 3.5 h and 5 h.
After burning for 2 h, the lengths of the
ca ndles become equal in length. What
fraction of the long candle’s height was the
short candle initially?
[NTSE 2013]
5
(B)
7
3
ANSWER KEY
1.
D
2.
B
3.
D
4.
D
5.
C
6.
B
7.
C
8.
A
9.
C
10.
D
11.
B
12.
B
13.
A
14.
B
15.
C
16.
17.
C
18.
C
19.
B
20.
A
22.
D
23.
A
24.
C
25.
C
26.
A
27.
C
28.
B
29.
C
30.
A
31.
C
32.
C
33.
B
34.
A
35.
C
36.
A
37.
B
38.
B
39.
B
40.
C
41.
C
42.
B
43.
A
44.
B
45.
D
46.
A
47.
D
48.
B
49.
D
50.
B
51.
A
52.
A
53.
C
54.
B
55.
D
56.
B
57.
D
58.
A
59.
D
60.
A
61.
A
62.
B
63.
A
64.
C
65.
C
66.
C
67.
C
68.
B
69.
C
70.
C
71.
B
72.
A
73.
B
74.
C
75.
D
76.
A
77.
D
78.
B
79.
C
80.
A
81.
A
82.
D
83.
D
84.
B
(B) 6n + 3
85.
B
86.
D
87.
A
88.
B
(C) 8n + 3
89.
B
90.
B
91.
D
92.
C
(D) 4n + 1 but may not be 8n + 1
93.
D
94.
D
3
5
(D)
21.
4
5
I left home for bringing milk between 7 am
and 8 am. The angle between the hour hand
and the minute hand was 90°. I returned
home between 7 am and 8 am. Then, also
the angle between the minute hand and
hour hand was 90°. At what time (nearest
to second) did I leave and return home?
[NTSE 2013]
(A)
(B)
(C)
(D)
7
7
7
7
h
h
h
h
18
19
20
21
min
min
min
min
35
24
42
49
s
s
s
s
and
and
and
and
7
7
7
7
h
h
h
h
51
52
53
54
min
min
min
min
24
14
11
33
s
s
s
s
The square of an odd integer must be of the
form
[NTSE 2013]
(A) 6n + 1
Q.93
41616
(B) 23.232323
(C)
(C)
Q.92
Which of the following is an irrational
number?
[NTSE 2013]
Which of the following numbers is the fourth
power of a natural number? [NTSE 2013]
2
(A)
7
Q.91
Q.94
The value of 1.34 4 .12 is
(A)
Q.89
Page # 109
a b
2
b
a
2
is
[NTSE 2013]
(A) always zero
(B) never zero
(C) positive if and only, if a > b
(D) positivel only, if a
b
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WORK, LIFE AND LEISURE
WORK, LIFE & LEISURE
CHARACTERISTICS OF THE CITY
1.
2.
Town and cities that first appeared along river valleys, such as Ur, Nippur and Mohenjodaro, were larger
in scale than other human settlements. Ancient cities could develop only when an increase in food
supplies made it possible to support a wide range of non-food producers. Cities were often the centres
of political power, administrative network, trade and industry, religious institutions, and intellectual
activity, and supported various social groups such a artisans, merchants and priests.
Cities themselves can vary greatly in size and complexity. They can be densely settled modern-day
metropolises, which combine political and economic functions for a entire region, and support very
large populations. Or they can be smaller urban centres with limited functions.
The industrialisation and the rise of the Modern city in England:
The early industrial cities of Britain such as Leeds and Manchester
attracted large number of migrants to the textile mills set up in the
late eighteenth century. In 1851, more than three-quarters of the
adults living Manchester were migrants from rural areas.
Now let us look at London. By 1750, one out of every nine people
of England and Wales lives in London. It was a colossal city with a
population of about 675000. Over the nineteenth century. London
continued to expand. Its population multiplied fourfold in the
70 years between 1810 and 1880, increasing 1 million to about 4
million.
The city of London : The city of London was a powerful magnet
for migrant populations, even though it did not have large factories.
‘Nineteenth century London’, says the historian Gareth Stedman
Jones, ‘was a city of clerks and shopkeepers, of small masters and
skilled artisans, of growing number of semi skilled and sweated
outworkers, of soldiers and servants, of casual labourers, street
sellers, and beggar’. Apart from the London dockyards, five major
types of industries employed large numbers clothing and footwear,
wood and furniture, metals and engineering, printing and stationary,
and precision products such as surgical instruments, watches,
and objects of precious metal. During the First World War
The growth of London,
(1914-18) London began manufacturing motor cars and electrical
a map showing its population
goods, and the number of large factories increased until they
in four different years.
accounted for nearly one-third of all jobs in the city.
In the mid-nineteenth century. Henry Mayhew wrote several volumes on the land on labour and
compiled long lists of those who made living from crime. Many of whom he listed as ‘criminals’ were in
fact poor people who lived by stealing lead from roofs, food from shops, lumps of coal, and clothes
drying on hedges. There were others who were more skilled at their trade, expert at their jobs.
They were cheats and tricksters, pickpockets and petty thieves crowding the streets of London.
In an attempt to discipline the population, the authorities imposed high penalties for crime and offered
work to those who were considered the ‘deserving poor’.
With technological developments, women gradually lost their industrial jobs, and were forced to work
within household. The 1861 census recorded a quarter of million domestic servants in London of whom
the vast majority were women, many of them recent migrants. A large number of women used their
homes to increase family income by taking in lodgers or through such activities as tailoring, washing or
matchbox making. However, there wa s a change once again in the twe nt ieth ce ntury.
As women got employment in wartime industries and offices, they withdraw from domestic service.
Large numbers of children were pushed into low-pad work, often by their parents. Andrew Means, a
clergyman who wrote The Bitter Cry of outseast London in the 1880s, showed why crime was more
profitable than labouring in small underpaid factories. A child seven years old is easily known to make
10 shillings 6 pence a week from thieving ... Before he can gain as much as the young thief (a boy)
must make 56 gross of matchboxes a week, or 1,296 a day. It was only after the passage of the
compulsory Elementary Education Act in 1870 and the factory acts beginning from 1902, that children
were kept out of industrial work.
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WORK, LIFE AND LEISURE
3.
Housing : For a while the better-off city dwellers continued to demand that slums simply be cleared
away. But gradually a larger and larger number of people began to recognise the need for housing for
the poor. What were the reasons for this increasing concern ?
A Stranger's Home, The Illustrated London New, 1870.
First, the vast mass of one-room houses occupied by the poor were seen as a serious threat to public
health; they were overcrowded, badly ventilated lacked sanitation.
Second, there were worries about fire hazards created by poor housing.
Third, there was a widespread fear of social disorder, especially after the Russian Revolution in 1917.
Workers mass housing schemes were planned to prevent London poor from turning rebellious.
Rat-trap seller, cartoon by
Rowlandson, 1799
A London slum in 1889.
For the poor, the street often was the only
place for rest, leisure and fun. The Illustrated
Lond News, 1856.
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4.
WORK, LIFE AND LEISURE
Clearing London : The congestion in the nineteenth-century
industrial city also led to a yearning for clean country air. Many
wealthy resident of London were able to afford a holiday home in
the countryside. Demands were made for new ‘lungs’ for the city,
and some attempts were made to bridge the difference between
city and countryside through such ideas as the Green Belt around
London.
Between two world wars (1919-39) the responsibility for housing
the working classes was accepted by the British state, and a
million houses, most of them single-family cottages, were built by
local authorities. Meanwhile, the city had extended beyond the
range where people could walk to work, and the development of
suburbs made new forms of mass transport absolutely necessary.
5.
Transport in the City : The very first section of the Underground
in the world opened on 10 January 1863 between Paddington and
Farrington Street in London. On that day 10,000 passengers were
New Earswick,
a garden suburb
carried, with trains running every ten minutes. By 1880 the expanded
train service was carrying 40 million passengers a year. At first
people were afraid to travel underground. This is what one
newspaper reader warned :
To make approximately two miles of railway, 900 houses had to be destroyed. Thus the London tube
railway led to a massive displacement of the London poor, especially between the two world wars.
Yet the Underground eventually became huge success. By the twentieth century, most large metropolises
such as New York, Tokyo and Chicago could not do without their well functioning transit system.
As a result, the population in the city became more dispersed. Better planned suburbs and good railway
network enabled large number to live outside central London and travel to work.
Railway lines being laid in London,
Illustrated Times, 1868.
Cows on the streets of London,
The Graphic, 1877
SOCIAL CHANGE IN THE CITY
Ties between members of households loosened, and among the working class the institution of marriage
tended to break down. Women of the upper and middle classes in Britain, on the other hand, faced
increasingly higher levels of isolation, although their lives were made easier by domestic maids who
cooked, cleaned and cared for young children on low wages.
Women who worked for wages had some control over their lives, particularly among the lower social
classes. However, many social reformers felt that the family as an institution had broken down, and
needed to be saved or reconstructed pushing these women back into the home.
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WORK, LIFE AND LEISURE
1.
Men, Women and Family in the City : Men and women did not have equal access to this new urban
space. As women lost their industrial jobs and conservative people railed against their presence in
public spaces, women were forced to withdraw into their homes. The public space became increasingly
a male preserve, and the domestic sphere was seen as the proper place for women. Most political
movements of the nineteenth century, such as Chartism (a movement demanding the vote for all adult
males) and the 10-hour movement (limiting hours of work in factories), mobilised large numbers of men.
Only gradually did women come to participate in political movements for suffrage that demanded the
right to vote for women, or for married women’s rights to property (from the 1870s).
By the twentieth century, the urban family had been transformed yet again, partly by the experience
of the valuable wartime work done by women, who were employed in large numbers to meet war
demands. The family now consisted of much smaller units.
2.
Leisure and Consumption : For wealthy Britishers, there had long been an annual ‘London Season’.
Several cultural events, such as the open the theatre and classical music performances were organised
for a elite group of 300-400 families in the late eighteenth century. Meanwhile, working classes met in
pubs to have a drink, exchange news and sometimes also to organise for political action.
Many new types of large-scale entertainment for the common people came into being, some made
possible with money from the state. Libraries, art galleries and museums were established in the
nineteenth century to provide people with a sense of history and pride in the achievements of the
British. At first, visitors to the British Museum in London numbered just about 15,000 every year.
A famous London resort,
painting by T.E. Turner, 1923
POLITICS IN THE CITY
In the severe winter of 1886, when outdoor work came to a standstill, the London poor exploded in a
riot, demanding relief from the terrible conditions of poverty. Alarmed shopkeepers closed down their
establishements, fearing the 10,000 strong crowd that was marching from Deptford to London. The
marchers had to be dispersed by the police. A similar riot occurred in late 1887; this time, it was
brutally suppressed by the police in what came to be known as the Bloody Sunday of November 1887.
Two years later, thousands of London’s dockworkers went on strike and marched through the city.
According to one writer, ‘thousands of the strikers had marched through the city without a pocket
being picked or window being broken....’ The 12-day strike was called to gain recognition for the
dockworkers’ union.
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WORK, LIFE AND LEISURE
THE CITY IN THE COLONIAL INDIA
The pace of urbanisation in India was slow under colonial rule. In the early twentieth century, no more
than 11 percent of Indians were living in cities. A large proportion of these urban dwellers were
resident of the three Presidency cities. These were multi-functional cities, they had major ports,
warehouses, homes and offices, army camps, as well as educational institutions, museums and libraries.
Bombay was the premier city of India. It expanded rapidly from the late nineteenth century,
its population going up from 644,405 in 1872 to nearly 1,500,000 in 1941.
A bustling sreet in Null Bazaar, Bombay,
photograph by Raja Deen Dayal, late
nineteenth century.
1.
Bombay the Prime city of India ? : Bombay was a group of seven islands under Portuguese control.
In 1661, control of the islands passed into British hands after the marriage of Britain’s King Charles II to
the Portuguese princess. The East India Company quickly shifted its base from Surat, its principal
western port, to Bombay.
Later in the nineteenth century, the city functioned a port through which large quantities of raw
materials such as cotton and opium would pass. Gradually, it also became an important administrative
centre in western India, and then, by the end of the nineteenth century, a major industrial centre.
A view of Bombay, 1852.
2.
Work in the City : The city quickly expanded. With the growth of trade in cotton and opium, large
communities of traders and blankers as well as artisans and shopkeepers came to settle in Bombay.
The establishment of textile mills led to fresh surge in migration.
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WORK, LIFE AND LEISURE
The first cotton textile mill in Bombay was establish in 1854. By 1921, there were 85 cotton mills with
about 146,000 workers. Only about one-fourth of Bombay’s inhabitants between 1881 and 1931 were
born in Bombay the rest came from outside. Large numbers flowed in from the nearby district of
Ratnagiri to work in the Bombay mills.
Women formed as much as 23 per cent of the mill workforce in the period between 1919 and 1926.
After that, their numbers dropped steadily to less than 10 per cent of the total workforce, By the late
1930s, women’s jobs were increasingly taken over by machines or by men.
3.
A map pf Bombay in the 1930s
showing the seven islands and
the reclamations.
Housing and Neighbourings : Bombay was a crowded city. While every Londoner in the 1840s
enjoyed an average space of 155 square yards, Bombay had a mere 9.5 square yards. By 1872, when
London has a average of 8 persons per house, the density in Bombay was a high as 20. From its earliest
days. Bombay did not grow according to any plan, and houses, especially in the Fort area, were
interspersed with gardens. The Bombay First area which formed the heart of the city in the early 1800s
was divided between a ‘native’ town, where most of the Indians lived, and European or ‘white’ section.
Many families could reside at a time in a tenement. The Census of 1901 reported that the mass of the
island’s population or 80 per cent of the total, resides in tenements of the one room; the average
number of occupants lies between 4 and 5 ....’ High rent forced workers to share homes, either with
relatives or caste fellows who were steaming into the city. People had to keep the windows of their
rooms closed even in humid weather due to the ‘close proximity of filthy guttes, privies, buffalo stables
etc.’ Yet though water was scarce, and people often quarrelled every morning for a turn at the tap,
observers found that houses were kept quite clean.
The homes being small, streets and neighbourhoods were used for a variety of activities such as
cooking, washing and sleeping. Liquor shops and akbaras came up in any empty spot. Streets were
also used for different types of leisure activities. Parvathibai Bhor recalled her childhood years in the
early twentieth century this way. ‘There was an open space in the middle of our four charts. There the
magicians, monkey players or players or acrobats used to regularly perform their acts. The Nandi bull
used to come. I used to be especially afraid of the Kadaklakshmi. To see that they had to beat
themselves on their naked bodies in order to fill their stomachs frigntened me’. Finally, chawls were also
the place for the exchange of news about jobs-strikes riots or demonstrations.
Caste and family groups in the mill neighbouring were headed by someone who was similar to a village
headman. Somet imes, the jobber in t he mills could be the local neighbourhood leader.
He settled disputes, organised food supplies or arranged informal credit. He also brought important
information on political developments.
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WORK, LIFE AND LEISURE
Chawl on Kalbadevi Road built in
the early twentieth century.
4.
Land Reclamation in Bombay : The need for additional commercial space in the mid-nineteenth
century led to the formulation of several plans, both by government and private companies, for the
reclamation of more land from the sea. Private companies became more interested in taking financial
risks. In 1864, the Back Bay Reclamation Company won the right to reclaim the western foreshore from
the tip of Malabar Hill to the end of Colba. Reclamation often meant the levelling of the hills around
Bombay. By the 1870s, although most of the private companies closed down due to the mounting cost,
the city had expanded to about 22 square miles. As the population continued to increase rapidly in the
early twentieth century, every bit of the available area was built over and new areas were reclaimed
from the sea.
5.
Bombay as the City of Drams : The world of Cinema and culture : Many Bombay films deal with the
arrival in the city of new migrants, and their encounters with the real pressures of daily life. Some
popular songs from the Bombay film industry speak of the contradictory aspects of the city. In the film
CID (1956) the hero’s buddy sings, ‘Ai dil hai muskil jeena yahan : zara hatke zara bachke ye hai
Bomaby meri Jaan’ (My heart, it is difficult to live here ! more over a little, take care of yourself this is
Bombay my love). A slightly more disillusioned voice sings in Guest house (1959); Jiska juta usika sar, dil
hai choota bada shahar, ye hai tumahri Bombay; (Bombay, you city what a place ! Here one gets
beaten with one’s own shoes ! The city is big but people’s hearts are small).
Most of the people in the film industry were themselves migrant who came from cities like Lahore,
Calcutta, Madras and contributed to the national character of the industry. Those who came from
Lahore, then in Punjab, were especially important for the development of the Hindi film industry. Many
famous writers, like Ismat Chughtai and Saadat Hasan Manto, were associated with Hindi cinema.
CITIES AND THE CHALLENGES OF THE ENVIRONMENT
The widespread use of coal in homes and industries in nineteenth century. England raised serious
problems. In industrial cities such as Leeds, Bradford and Manchester, hundreds of factory chimneys
spewed black smoke into the skies. People joked that most inhabitants of these cities grew up believing
that the skies were grey and all vegetation was black ! Shopkeepers, homeowner and other complained
about the black fog that discended on their towns, causing bad tempers, smoke-related illnesses,
and dirty clothes.
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WORK, LIFE AND LEISURE
When people first joined campaigns for cleaner air, the goal was to control the nuisance through
legislation. This was not at all easy, since factory owners and stead engine owners did not want to
spend on technologies that would improve their machines. By the 1840s, a few towns such as Derby,
Leeds and Manchester had laws to control smoke in the city. But smoke was not easy to monitor or
measure, and owners go away with small adjustments to their machinery that did nothing to stop the
smoke. Moreover, the Somke Abatement Act of 1847 and 1853, as they were called, did not always
work to clear the air.
Calcutta had a long history of air pollution. Its inhabitants inhaled grey smoke, particularly in the
winter. Since the city was built on marshy land, the resulting fog combined with smoke to generate
thick black smog. High levels of pollution were a consequence of the huge population that depended on
dung and wood as fuel in their daily life. But the main polluters were the industries and establishments
that used steam engines run on coal.
IMPORTANT TERMS
1.
Many decades after the beginning of the industrial revolution, most western countries were largely
rural till 1850.
2.
More than three quarters of the adults living in Manchester were migrants from rurals areas till 1851.
3.
One out of every nine people of England and Wales lived in London by 1750.
4.
The population of London multiplied four fold between 1810-80.
5.
The compulsory Elementary Education Act was passed in 1870.
6.
The factory Acts beginning from 1902.
7.
The responsibility for housing the working class was accepted by the British state in 1919-39.
8.
‘Charls Dickens wrote about the massive destruction in the process of construction in 1848.
9.
The London poor exploded in riot demanding relief in 1886.
10.
A similar riot occurred in late 1887.
11.
One fifth of the streets of Paris were Haussmann’s creation by 1870.
12.
Bankim Chandra Chattopadhyay wrote short sketches on urban life in Calcutta in 1962.
13.
After the marriage of Britain’s King Charles II to the Portuguese princess the control of Bombay was
transferred to Britishers in 1661.
14.
Bombay became the capital of Bombay Presidency in 1819.
15.
About 1/4 of Bombay’s inhabitants were born in Bombay, the rest came from outside between 1881 and
1931.
16.
Bombay was built a dry dock between 1914-18.
17.
The film industry employed 520,000 people by 1987.
18.
Calcutta became the first city to get smoke nuisance legislation in 1863.
19.
The smoke abatement Act of 1847 and 1853.
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Exercise - I
WORK, LIFE AND LEISURE
UNSOLVED PROBLEMS
A.
VERY SHORT ANSWER TYPE QUESTIONS
B.
SHORT ANSWER TYPE QUESTIONS
Q.1
What is metropolis ? Give an examples of
Q.1
Examine the historical processes involved in
metropolis in India.
Q.2
Name two industrial cities in England in 19th
the development of cities.
Q.2
Mention the steps taken to clean up London.
Q.3
Explain the evolution of Bombay as one of the
century.
Q.3
Mention two steps t aken by the London
major cities of India.
authorities to discipline its population.
Q.4
Q.4
Describe the Bombay fort area.
Q.5
What is referred to as Chawls in Bombay ?
Why were the slams considered to be threat
to public for London ?
With which kind of London housing can these
Q.5
Why were the slums considered to be threat
be compared ? How are these similar ?
to public health ?
Q.6
Q.6
Examine the effects of air pollution on Calcutta.
Q.7
By whom was the concept of a Garden city
Name two Acts passed in England to keep the
children out of industrial world.
first developed ? What were the main features
Q.7
When by whom was the first movie made in
of the proposed Garden city ?
Bombay ? What did the movie depict ?
Q.8
Name the first proper Hindi movie. By whom &
Q.8
construction of underground railways.
when was this movie made ?
Q.9
Mention the problems raised in England in 19th
Q.9
Q.10
Q.11
Q.10
Q.11
Under what circumstances were the ancient
Examine the ne w ty pes of large scale
ent ert ainment fo r the common people
When was the Rent Act passed in Bombay ?
introduced in 19th century.
What was its out come ?
Q.12
What were the mode of entertainment in the
18th century England ?
Which two stations of London were connected
by the first underground railways ?
How was the family life transformed in an
industrial city of London ?
century due to widespread use of coal in
industrial cities.
Examine the difficulties faced by people due to
Q.12
Why was the expansion of the city of Bombay
difficult ? Mention any one way adopted to
cities developed ?
develop the city.
Q.13
Name four industries which employed largest
member of people is London in early 20th
Q.13
environment ?
century ?
Q.14
What is meant by temperance movement ?
Q.14
When was the Bombay Improvement Trust
est abli she d ? W hat was its imm ediat e
When did Bombay film industry make its first
appearance ?
What was its main aim ?
Q.15
How do es urba nisation pose a threat to
Q.15
Why police was worried for the law and order
of London ?
achievement ?
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WORK, LIFE AND LEISURE
Q.16
Q.17
Mention various measures which were taken
Q.10
the cost of ecology and environment? Explain,
centuries.
giving examples of industrial cities of England
[Delhi 2009]
in the nineteenth century.
How far was the underground railway able to
solve trasnport problems as well as housing
Q.11
crisis in London in the nineteenth century?
Why is Mumbai (Bombay) known as the city of
dreams? Give three reasons.
[Delhi 2008]
Explain any three reasons for which the
population of the London City expanded over
the nineteenth century.
[O.I. 2008]
Q.18
How is urban development directly related to
to decongest London in the 19th and 20th
Q.12
[O.I. 2009]
Explain the social changes which led to the
need for the underground railways in London.
[Delhi 2010]
[A.I. 2007]
C.
LONG ANSWER TYPE QUESTIONS
Q.1
“London was powerful magnet for largest
Q.13
What was the tradition of 'London Season'?
Explain different forms of entertainment that
came up in nineteenth century England to
population”. Explain.
Q.2
provide leisure activities for the people.
How were women employed in London beyond
[A.I. 2011]
19th century ? How did the situation change
after 20th century.
Q.3
Q.14
What were the reasons for concern behind
Describe the means of entertainment available
in England in the Nineteenth Century.
providing housing for poor in London ?
Q.4
[RBSE 2013]
What were chartist movement and Ten Hour
Movement ?
Q.5
How do we distinguish between cities on the
one hand and towns and villages on the other?
Q.6
Explain the life style o f wo rkers of t he
mid-nineteenth century in Britain. [A.I. 2010]
Q.7
How did the development of cities influence
the ecology and environment in late 19th
century? Explain by giving an example of
Calcutta.
Q.8
[Delhi 2011]
Explain any three reasons for the increasing
concerns about the need for housing for the
poor in London after the Industrial Revolution.
[A.I. 2011]
Q.9
Describe in brief the development of Bombay
(Mumbai) as the 'Prime City' of India.
[A.I. 2012]
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WORK, LIFE AND LEISURE
Exercise - II
Q.1
NTSE/OLYMPIAD PROBLEMS
What was not a reason for providing mass
(A) Concern for the poor
(A) 1996
(B) 1897
(B) Fear of Social disorder
(C) 1898
(D) 1900
Q.11
passed in -
Which movie did Dada Sahab Phalke make ?
(A) 1860
(B) 1870
(A) CID
(C) 1880
(D) 1890
Q.12
(D) Tezab
Q.5
Bombay was first under whose control ?
(A) Portuguese
(B) English
(C) French
(D) Dutch
Q.13
(B) Bombay
(C) Calcutta
(D) Lucknow
Q.14
in a planned manner ?
Q.6
Q.7
Q.8
(B) Madras
(C) Signapore
(D) Lucknow
Q.15
(B) 1887
(C) 1888
(D) 1889
Q.16
When was the Rent Act passed in Bombay ?
(A) 1910
(B) 1918
(C) 1920
(D) 1922
(C) Jaipur
(D) Calcutta
Bombay was built a ............... between
(A) Harbour
(B) Capital
(C) Seaport
(D) Dry dock
The film industry employed .............. people
(A) 500000
(B) 520,000
(C) 540,000
(D) 560,000
Bombay became the capi tal of Bo mbay
Presidency in -
When was the first movie made in India ?
(A) 1886
(B) Bombay
by 1987.
Which of the following cities has developed
(A) Delhi
(A) Delhi
1914-18
Which of the following is not a Presidency city?
(A) Madras
................ became the first city to get smoke
nuisence legislation in 1863.
(C) Raja Harishchandra
Q.4
The compulsory Elementary Education Act was
(D) All the above
(B) Guest house
Q.3
The city of Bombay improvement trust was
established in -
(C) Threat to public health
Q.2
Q.10
housing schemes for the workers ?
(A) 1817
(B) 1818
(C) 1819
(D) 1820
What is the meaning of urbanization?
(A) Development of a city or town
(B) People migrating from rural to urban
(C) Expansion of city
Who developed the concept of a Garden city?
(D) All these
(A) Ebenezer Howard
(B) Clive
ANSWER KEY
(C) Pluto
1.
A
2.
C
3.
A
4.
D
5.
C
6.
A
7.
B
8.
A
9.
B
10.
C
11.
B
12.
D
13.
D
14.
B
15.
C
16.
D
(D) John Mill
Q.9
Name the Industrial city of England in 19th
century (A) London
(B) Leeds
(C) Washington
(D) None of these
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