Download CLASS 10TH ASSIGNMENT PHYSICS

PHYSICS
NUMERICAL QUESTIONS
CLASS – X
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A heater joined in parallel with a 60 W bulb is connected to the mains. If the 60 W bulbs is replaced
by a 100 W bulbs, will the rate produced by the heater be more or less or remain the same?
Specific resistances of copper, silver and constantum are 1.18  106  1.18 x 10 cm, 1  106  cm
and 48  10 6  cm respectively. Which is the best electrical conductor and why?
A current of 5.0 A flows through an electric press of resistance 44  . Calculate the energy consumed
by the press in 5 minutes.
Write the least possible value that can be obtained by connecting three resistors 2  , 3  , and 5  .
What is the maximum value of resistance that can be obtained by using three resistors 2  ,
3  , and 5  .
A small heating element, connected to a 10 V. d.c. supply draws a current of 5 A. How much electric
power is supplied to the heater?
A steady current is passed through a copper voltameter for 10 minutes. The mass of copper
deposited is 0.0128 gram. Calculate the value of current passing through the voltameter. [E. C. E. of
Cu = 0.00032 g/c].
In a copper planting experiment, 8.25 gms of copper is deposited in for one and a half hour. What is
the ammeter reading connected in series? Given, One Faraday = 96400 C, atomic mass of copper =
63.54 g.
9.
A heater coil is rated 100 W, 200 V. It is cut into two identical parts. Both parts are
connected together in parallel to the same source of 200 V. Calculate the energy liberated
per second in the new combination.
10. Calculate the equivalent resistance of the resistance network between the points A and B as
shown in the figure when switch S is closed.
12 V
8V
A
B
12 V
8V
11. V-I graph for a metallic wire at two different temperatures T1 and T2 as shown in the
following figure. Which of the two temperatures is higher and why?
T1
I
T2
V
12.
Calculate the electrical conductivity of the material of a conductor of length 3 m, are of cross section
0.002 mm² having a resistance of 2 V .
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14.
A 10V thick wire is stretched so that its length become three times. Assuming that there is no change
in its density on stretching, calculate the resistance of new wire?
15.
16.
Calculate the energy supplied by 100 kW of power in one hour.
A metallic wire of length 1 m is stretched to double its length. Calculate the ratio of its initial and
final resistance assuming that there is no change in its density on stretching.
Calculate the distance between two protons such that the electrical repulsive force between them is
equal to the weight of either.
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18.
Determine the volts drop across the resistor R in the circuit given below with E = 60 V, R1 = 18 V ,
R2 = 10 V
, R3 = 5 V , R4 = 10 V .
R1
60 V
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R3
R2
R3
A house is fitted with ten 60 W lamps. How many units of electrical energy are consumed by lighting
the lamps for a month of 30 days at a rate of 5 hours a day?
An electric heater is used everyday for 120 minutes. The electricity bill for 30 days is 60 units.
Calculate the power of the electric heater.
A 60 W electric lamp gives off energy in the form of light at a rate of 7.5 J per second. What
percentage of energy does the lamp transform into light energy?
A 220 W bulb is lighted for two hours. How much energy is consumed?
Calculate the coulombic force between two  particles separated by a distance 3.2 x 10–15m.
Define coulumb. How many electrons will have a total electric charge of 1 C?
Calculate the Coulombic force between two protons separated by a distance of 1.6 x 10–15m.
How many electrons are there in – 10 C of charge?
The filament of an electric lamp draws a current of 0.4 amperes, which lights for 3 hours. Calculate
the amount of charge.
How much current will an electric heater draw from a 220 volt line, if the resistance of the heater is
50 ohms?
If 2V, 3 V and 5 V are in parallel, will the value of total resistance be less than 2 or greater than 5 or
lie between 2 V and 5 V ? Explain.
Write the relation connecting power, current and voltage. Using it find the power of a torch bulb
rated at 2.5 volt. 500 mA. Also find its resistance.
A steady current is passed for a certain time through three voltameters connected in series : a
copper voltameter (Cu electrodes in CuSO1 ), a silver voltameter (Ag electrodes in AgNO2) and an
iron voltameter (Fe electrodes in FeCI3). The mass of copper deposited on the cathode of the first
voltameter is 473.1 g. Find out the masses of silver and iron deposited on the respective cathodes of
the other two voltameters. Given that the relative atomic masses of Cu, Ag and Fe are 63.54, 107.9
and 55.85 and their valecies are 2, 1 and 3 respectively.
Two lamps, one rated 100 W at 220 V and the other 60 W at 220 V are connected in parallel to a 220
V supply. What current is drawn from the supply line?
A heater coil connected to a 220 V has a resistance of 150 ohms. How long will it take for this coil to
heat 1 kg of water from 20°C to 60°C, assuming that all heat is taken up by water?
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A 40 watt lamp requires a 0.182 A of current at 220 volts, while a 60 watt lamp requires 0.272 A of
current at 220 volts. If a 40 watt lamp and a 60 watt lamp are connected in series with a 220 volt
line, how many amperes of current will flow through each lamp?
Draw a schematic diagram of a circuit consisting of a battery of four 2 V cells, a 5 ohm resistor, an 8
ohm resistor, a 12 ohm resistor, and a plug key, all connected in series.
Redraw the circuit of the previous quesiton, putting in an ammeter to measure the current through
the resistor and a voltameter to measure the volatge across the 12 ohm resistor. What would be the
readings in the ammeter and the voltameter?
A copper wire has a diameter of 0.5 mm and a resistivity of 1.6 ohm cm. How much of this wire
would be necessary to make a 10 ohm coil?
Two protons separated by 1 m experience a repulsive force of F newton. If two alpha particles are
placed at a separation of ‘2m’, find the repulsive force.
39.
Show how ammeter and voltameter are connected when 2 A current flows through a 10V
resistance with a battery of 20 volts.
40.
A rod has a resistivity of 2 x 10–3V m. If its length is doubled and area is halved, what is the new
resistivity?
41.
When two resistors 2 V and 5 V are placed in a network, find the equivalent network in (i) Serious
and (ii) parallel.
In the circuit shown below, find the current drawn and potential difference between A and B.
42.
3V
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6V
(
)
K
3V
A
B
Prove that the equivalent of three resistors R1 , R2 and R3 in series R1+ R2 + R3.
When two resistors of 10V are placed (i) in parallel and (ii) in series. Find the current flowing them
with a potential source of 5 volt.
Find the equivalent resisting using the following circuit with the keys (i) closed (ii) open.
10 V
A
5V
B
S
5V
10 V
46.
When three resistors R1, R2 and R3 are in parallel to a source of V, express how the current and
potertial in them vary? Also find equivalent resistance.
47.
When three resistors 5 V , 10 V, and 15 V are given to you, find the least and maximum possible value
of resistance that can be using them.
A 100 W electric bulb is lighted for 2 hours daily and four 40 W bulb are lighted for 4 hours
everyday. Calculate the energy consumed (in kWh) in 30 days.
Calculate the number of electrons which pass through the filament of a 12 W, 6 V lamp in one
minute.
Two resistance connected to 100 v supply in parallel draw 10 A current from the supply. If the
power dissipation in one resistor is 600 W, find
(i) power dissipation in the other, (ii) resistance of each.
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51.
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In a household, an electric bulb of 100 W is used for 10 hours and an electric heater of 1000 W for 2
hours everyday. Calculate the cost of using the bulb and the heater for 30 days, if the cost of one
unit of electrical energy is two rupees.
In a household, 5 tubelights each of 40 W are used for 5 hours and an electric press of 500 W for 4
hours everyday. Calculate the cost of using tubelights and the electric press for 60 days, if the cost of
1 unit of electrical energy is Rs. 2.50.
Define the term electochemical equivalent electrolyte. A copper voltameter and an ammeter are
connected in series with a battery through a resistor. In 50 minutes, 0.99 g copper is deposited on
the plate. The ammeter reads 0.95 A. Calculate the error in the reading of ammeter. Chemical
equilavent of copper = 0.00033 g/c.
54.
A copper voltameter is in series with a heater coil of resistance 0.1V. A steady current flows in the
circuit for 20 minutes and a mass of 0.99 gm of copper is deposite at the cathode. If the
electrochemical equilavent of copper is 0.00033 g/c, calculate the heat generated in the coil.
55. A 100 W electric bulb is lighted for 2 hours everyday and five 40 W tubes are lighted for 4 hours
everyday. Calculate (i) the energy consumed for 60 days.
59. In a house, and electric bulb of 60 W is used for 15 hours and an electric heater of 750 W is used for
10 hours everyday. Calculate the cost of using the bulb and the heater for 30 days if the cost of 1
unit of electrical energy is two rupees.
60. One gram of coal on burning liberated 18 kJ of energy. How many kilograms of coal will produce as
much energy as an electric bulb of 200 W consumes in 10 hours?
61. In a factory, electric bulb of 500 W is used for 2 hours and electric motor of 0.5 horse power is used
for 5 hours everyday. Calculate the cost of using the bulb and motor for 30 days if cost of electrical
energy is three rupees per unit.
62. To deposit 0.5 kg of silver per hour on the cathode of a silver voltameter of resistance 0.70 milliohm,
how much potential difference must be maintained between the plates?
63.
In the circuit given below, if the resistors R1 ,R2 and R3 have the values 5V , 10 V and 30 V
respectively, connected to a battery of 12 volt. Calculate (i) the current through each resister, (ii) the
total current in the circuit, (iii) the total circuit resistance.
R1
R2
R3
12 V
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20.
Five dry cells of 1.5 volt each have internal resistance of 0.2, 0.3, 0.4, 0.5 and 12 ohms. When
connected in series, what current will these cells furnish 10 ohms resistance.
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) 0.5
2.5
6.75 11.0 15.0
Plot a graph between V and I and calculate the resisitance of the resistor.
Calculate the resistance of 1 meter of copper wire that has a cross sectional area of about 2 x 10–2
cm². Compare the value of this resistance with that of a flashlight bulb, which has a power rating 1
W and operates at 3 V. What does this comparison tell you?
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In a distance tube, the number of protons drifting a cross-section per second is 1.0 x 1018 , while the
number of electrons drifting in the opposite directions across another cross-section is 2.7 x 1018 per
second. If the supply voltage is 230 V, what is the effective resistance of the tube?
Two wires of equal length, one of aluminium and the other of copper, have the same resistance.
Which of the two wires is lighter? Hence, explain why aluminium wires are prefeffed for overhead
power cables. Relative density of Al = 2.7, that of copper = 8.9, resistivity of Al = 2.63 x 10–8V m and
that of copper = 1.72 x 10–8 w.m.
(i) State the fundamental laws of electrostatics.
(ii) Suggest two ways of charging a body.
State Coulomb’s law. Find the ratio of electrical repulsive force between a pair of electrons and
protons at a separation of 2 m?
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