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MAGNETIC EFFECTS OF ELECTRIC CURRENT
MAGNETIC EFFECTS OF ELECTRIC CURRENT
INTRODUCTION
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Motion of electric charges is defined as current. It has chemical and heating effects as we discussed in
the last chapter. It was found by Oersted that current also produces magnetic field. The origin of the magnetic
effect in our earth and the application of the magnetic field in various walks of life is discussed. All the
applications in magnetic field are with regard to the change in the strength of field or its effect. This is
highlighted by the principal of Electro-magnetic induction.
IMPORTANT TERMS AND CONCEPTS
1.
2.
3.
Lodestone. The black ore of iron (Fe3O4) called magnetite, capable of attracting similar pieces of iron is
called Lodestone. They are naturally existing magnets used by man to find the directions. Now-a-day we
use magnetic needles to find direction. The end pointing towards the geographic North is called North
pole and the South seeking pole is called South pole.
Basic laws of Magnetism.
(i)
There are two poles namely North pole and South pole.
(ii)
Like poles repel each other, while unlike poles attract each other.
Oersted’s experiment. H. C. Oersted, a Danish Physicist first noticed the magnetic effect of electric
current. According to him, a needle kept near the wire carrying current will deflect due to the magnetic
field produced. Any changes in direction of current will show variation in deflection.
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AB – Wire
M – Magnetic needle
V – Battery
A – Ammeter
Magnets. The smallest magnetic element can be built is called a magnet. It has two poles named North
and South pole. When it is hung using a string tied to its middle, the two poles will seek North and
South of Earth.
Magnetic field. Surrounding a magnet its influence is felt by any other magnetic element. It may be an
attractive or a repulsive influence. The strength is defined as the force experienced by unit magnetic
North pole placed at a point. It is measured in Tesla or Weber/m².
Magnetic field lines. When a bar magnet is placed on a cardboard and iron-filings are sprinkled, they
will arrange themselves in a pattern as shown below.
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MAGNETIC EFFECTS OF ELECTRIC CURRENT
They are said to align the field lines of the bar magnet. To picturise magnet field lines, follow the
following steps:
(i)
Bring the needle close to North pole and mark the tips of the needle.
(ii)
Move the compass such that, one end points the fixed farther point and place a point on the other end of
the needle.
(iii)
Repeat the steps till the South pole is reached.
(iv)
Join all these points to get a line and put an arrow to indicate directions.
(v)
Repeat the four steps to show many lines, which will resemble the orientation of iron fillings.
7.
Characteristics of Magnetic field lines.
(i)
The direction of the magnetic field is indicated by the arrow in the line at any point (Tangent).
(ii)
The field lines comes out of the North pole and get into the South pole (closed loops are formed).
(iii)
The strength of magnetic field is indicated by the closeness of the field lines. More the lines, more will
be the lesser the lines lesser will be the field strength.
(iv)
No two field will intersect each other-if they intersect there will be two different directions for field at
the same point which is not possible.
8.
Magnetic field around a current carrying straight conductor. Insert a wire carrying current through
a hole at the middle of a cardboard. When a current I is passed through the wire, surrounding the wire,
magnetic field will be created. When you springle iron fillings, on the board, they will all settle in
concentric rings. The direction of North pole is given by the arrow. Reversal current will reverse the
magnetic field.
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(i)
(ii)
(iii)
(iv)
(v)
Right hand Thumb rule. Hold the wire carrying current in your right hand, such that the thumb
indicates the direction of current, then the folded fingers will indicate the presence of magnetic field
(lines) surrounding the wire.
Magnetic field due to a small wire depends.
directly on the length of the wire,
directly on the current passing through the wire, and
inversely on the square of the current passing through the wire.
Magnetic field due to a current carrying circular wire. The field created due to a circular coil is
given by the figure,
The direction of field is perpendicular to the plane of the coil and directed inwards for the clockwise
current flowing. For anti-clockwise current, it will be flowing anti-clockwise. The field lines in circular
coil have the following characters:
Circular near the wire.
Straight at the centre
Field is perpendicular to the plane of the coil.
For larger areas, the field at the centre is uniform.
Field lines will enter into plane and leave the other. (Enter on the side with clockwise current).
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(i)
(ii)
(iii)
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MAGNETIC EFFECTS OF ELECTRIC CURRENT
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12.
13.
Clockwise
Anti clock-wise
Field enters into the plane
Field comes out
South pole
North pole
Solenoid. A coil of large number of turns closely wound on a hollow cylinder of insulated material or
otherwise is called a solenoid. The end of the solenoid having clockwise current will act as South polefield enters into, while the other end having anti-clockwise current will act as North pole-field comes
out. Thus, a solenoid acts as a normal magnet.
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Direction of field (Notation). To identify the direction of magnetic field the following diagrams can be
used:
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Magnetising a material. When a material is placed inside a coil carrying current, it will get magnetized.
A bunch of nails ore a iron rod placed along the axis of the coil can be magnetized by the current
allowed to pass through the coil. Once the current is put-off the magnetic field will also be lost. Such
magnets are called electro-magnets. If the rod is made of steel then the magnetism acquired will not be
lost even after the removal of current. Such magnets are called permanent magnets.
Permanent magnets are made of carbon steel, chromium steel, tungsten steel and some alloy like
Alnico and Nipermag.
Alnico is an alloy of aluminum, nickel, and cobalt. Nipermag is an alloy or iron, nickel, aluminum and
titanium. Permanent magnets are used in microphones, loudspeakers, electric clocks and many
measurement tools like speedometers, galvanometer, ammeter and voltmeter etc.
Force on current carrying conductor in Magnetic field. Ampere suggested that any current carrying
conductor when placed in a magnetic field will experience a force. When a current l passes through a
conductor of length l placed in perpendicular magnetic field B, the force experienced is given by F = IB.
It has confirmed that the direction of force is perpendicular to both the length and the magnetic field.
Fleming’s Left-Hand Rule. Stretch the first three fingers of the left hand mutually perpendicular to
each other such that the fore finger points the direction of magnetic field, the middle finger points the
direction of current, then the thumb will indicate the direction of force experienced by the conductor. It
is to be applied when the current and field are perpendicular to each other.
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MAGNETIC EFFECTS OF ELECTRIC CURRENT
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18.
19.
20.
21.
22.
Force on a charge. Similar to a conductor carrying current, a charge moving in a magnetic field will
always experience force in perpendicular direction. The force is given by F = qvB, when v and B are
perpendicular to each other.
Van Allen Belt. The region of trapped high charged particles near earth’s equator is called as Van Allen
Belt. It was discovered by James Van Allen.
Particle Accelerators. Charged particles can be accelerated by devices like Cyclotron, Synchrotron, etc.
by using the principle of a charged particle experiencing force.
Electric Motor. The device used to convert electrical energy to mechanical energy is called Electric
Motor. It is used in fans, machines, etc.
Working of an Electric Motor. Electric motor works on the principle of force experienced by a current
carrying conductor in a magnetic field. The two forces in the opposite sides are equal and opposite.
Since they act in different lines they bring rational motion.
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Electromagnetic Induction. According to factory, when a magnet is in motion relative to a coil
attached with a galvanometer, induced electric is set up in the coil. This idea of creation of current by
changing magnetic strength is called Electromagnetic Induction.
When North pole of a magnet is taken towards a coil with galvanometer, induced current will flow in
such a way that the North pole is created on the side of the magnet to oppose the change that produces
the current. When North pole is taken towards or South pole is taken towards, the galvanometer
deflection will be opposite. Faster the magnet is moved towards or away from the galvanometer, the
deflection in the galvanometer will be more in opposite directions.
When a coil connected with a galvanometer is placed, close to a coil connected with a battery and a key,
on switching ON or OFF, the galvanometer shows deflection.
Magnetic Flux. It is defined as the product of the magnetic field and the area through which magnetic
field passes perpendicularly.  = BA when field passes perpendicular to the plane of the coil. It is
measured in Weber.
Faraday’s Law. The rate at which the magnetic flux linked with a coil changes produces the induced
current. More the rate, more the current and vice versa.
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MAGNETIC EFFECTS OF ELECTRIC CURRENT
26.
Fleming’s Right hand Rule. Stretch the first three figures of the right mutually perpendicular to each
other such that ht fore finger gives the direction of magnetic field and the thumb points the direction of
the mention of a conductor then, the middle finger will give the direction of the induced current.
27.
Electric Generators. Generators works on the principle of Electro-magnetic Induction. It converts the
mechanical energy available into electrical energy. When a coil is rotated in a magnetic field, then there
will be induced current flowing in it. The direction of the induced current can be found using the right
hand Fleming’s Rule.
28.
Armature. The coil having many turns used in electric motor or generator is called Armature.
29.
Rings. In AC generator we use slip rings-full ring with which the ends of the coil are in contact. In DC
generator we use split rings-half rings with which the ends of the armature coil will be in contact.
30.
Brushes. Metallic contacts (carbon) in contact with external device and the rings.
31.
AC generator produces potential which reverses after every 180° rotation of the coil. The signal is
shown in the following way.
DC Generator produces signal in the same sense as shown below i.e., no reversal after 180° rotation.
This is done by using a Commutator.
V
t
t
t - Rotation angle
 - Angular frequency of rotation
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(i)
(ii)
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In India AC generator and uses reverses in 1/100 second or has a frequency of 50 Hz. Alternating
current is used for transmission since.
Loss of energy is less over large distance.
Conversion to needed potential is possible in AC transformers.
Electric Supply in House. Electrical supply to the house is supplied at 220 volts using two wires-one
using red and insulation cover for live wire and the other having black insulation called neutral wire.
Kilowatt Hour. Kilowatt hour is the commercial unit for electrical energy. In house a kilowatt hour
meter is used for measuring the energy consumed. All electrical appliances are connected with the
neutral wire, so that any wrong connection will inactive the device and save the device from destruction.
House-hold connection. We use parallel connection in the various electrical points in the house.
This is because,
(i)
Individual appliance can be operated at any time.
(ii)
All appliances will get the same potential difference of 220 volts needed for their operation.
Fuse Wire. It is safety wire connected in series in the live wire. In case of any large current supply or
malfunctioning in the electric connections, the fuse wire burns and disconnects the entire circuit from
the electrical supply. The fuse wire should have.
(i)
High resistance
(ii)
Low melting point.
Normally, the fuse wire is made of an alloy of copper and tin.
Fuse wires with varying capacity are available. The thickness of the wire increases the maximum safe
current that can flow through it. In India fuse for a current of 5A and 15A is used. For heavy
applications like geyser, heaters etc. 15A fuse is used, but for fan light and many other light types of
equipment 5A fuse wire is used. It is not proper to put a highly thick wire for low current appliances,
since the equipment may be damaged as a result of higher current.
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MAGNETIC EFFECTS OF ELECTRIC CURRENT
36.
Earth’s magnetic field. The existence of magnetic field around the earth was detected in 1600 by
English scientist, William Gilbert. It is imagined that a huge magnet is at the center of the earth. The
axis of this magnet is inclined at an angle of 17° to the axis of rotation of earth.
37.
True equator. Any line perpendicular to the axis of rotation of earth is called true equator.
38.
Magnetic axis. The line joining the earth’s magnet is called magnetic axis.
When a magnetic is suspended using a string, it will align along the North-South direction. The North of
magnet points geographic North. This is due to the presence of South pole of the earth’s pole of magnet.
Similarly the South pole of our magnet poles is called earth’s magnetic axis.
39.
Magnetic meridian. The perpendicular plane having the magnetic axis of freely suspended magnet is
called magnetic meridian.
40.
Geographic meridian. The perpendicular plane having the geographic axis-earth’s North and South
called geographic meridian.
41.
Declination (  ). The angle between the magnetic and geographic meridian is called declination.
42.
Dip or inclination (  ). The curvature of earth differs and brings magnetic field in different magnitude
at various points. So the horizontal and vertical are the two components at any point. The angle between
the horizontal component and the resultant field at the point is called dip or inclination. Angle of dip is
defined as the angle which the total intensity of the earth’s magnetic field makes with the horizontal
component of earth’s field.
43.
Horizontan Component of earth’s field. The strength of magnetic field along the surface of earth is
called horizontal component (BH).
Dip, Declination, BH are shown in the diagram below showing magnetic and geographic meridian from
the diagram, 
Declination,  – angle of dip.
B
Also tan   V Where BV , BH are vertical and horizontal components of earth's field.
BH
The angle of dip is more, i.e., 90° at the poles, since horizontal component is zero at poles. The
horizontal component of field alone exists in the equator and the vertical component is zero. So the
angle of dip in the equator is 0°.
44.
Transformers. Transformers are devices which work on the principal of electro-magnetic induction. It
has two coils namely, primary and secondary should be the same. So when potential is increased, current
will be decreased and vise versa. A transformer will not work in DC.
1 Mark Questions
What is the magnitude of induced current in the circular loop KLMN, of radius ‘r’ if the straight
wire PQ carries a steady current of magnitude ‘I’ ampere?
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How will the magnetic field intensity at the center of a circular coil carrying current change if the
current through the coil is doubled and the radius is halved?
In which directions would a compass needle align if taken a geographic (i) North and (ii) South.
Why does the acceleration of a bar magnet decreases, while falling through a solenoid, connected
to a closed circuit?
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MAGNETIC EFFECTS OF ELECTRIC CURRENT
5.
If the ratio of horizontal component of earth’s magnetic field to the resultant magnetic field at a
1
place is
, what is the angle of dip at that place?
2
6.
What is the angle of dip at a place where the horizontal and vertical components of earth’s
magnetic field are equal?
7.
Name the physical quantity whose S. I. unit is Wb-m². Is it a scalar or a vector quantity?
8.
The current through the wire PQ is increasing. In which direction does the induced current flow
in the closed loop?
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Give the direction of induced current in the wire loop, when the magnet moves forward as shown
in fig.
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An electron beam is moving vertically upwards. If it passes through a magnetic field which is
directed from South to North in a horizontally plane, then in which direction will the beam be
deflected?
Under what condition is the force acting on a change moving through a uniform magnetic field
minimum?
A bar magnet falls from height ‘h’ through a metallic ring. Will its acceleration be equal to ‘g’?
Give reason for your answer.
What is the value of angle of dip at any place situated on the magnetic equator of the earth?
Name the quantity which has unit Weber/ampere.
Does a step-up transformer contradict the principle of conservation of energy?
Why can’t a transformer be used to step up DC voltage?
Can two magnetic lines of force ever intersect? Justify your answer.
Name the elements of earth’s magnetic field.
A small magnet is pivoted to move freely in the magnetic meridian. At which place on the earth
will the magnet be vertical?
What is angle of declination?
What is geo-magnetic equator?
How does dip angle change as one moves from magnetic equator to the pole?
Why is necessary to earth the metallic appliances?
What is the meaning of short circuiting?
Explain briefly the term “Overloading”.
On what factors the force experienced by a conductor carrying current in a uniform magnetic
field depend.
What are the S. I. unit of (i) Magnetic flux (ii) Magnetic field strength.
How the Gauss related to Weber/m²?
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CONTACT FOR MATHEMATICS GROUP/HOME COACHING FOR CLASS 11TH 12TH BBA,BCA,
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EMAIL:7 [email protected] web site www.badhaneducation.in
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CONTACT FOR COACHING MATHEMATICS FOR 11TH 12TH NDA DIPLOMA SSC CAT SAT CPT
CONTACT FOR ADMISSION GUIDANCE B.TECH BBA BCA, MCA MBA DIPLOMA AND OTHER COURSES 09810144315
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MAGNETIC EFFECTS OF ELECTRIC CURRENT
29.
Name the first material noticed to have magnetic property.
30.
How can you identify the poles of a magnet?
31.
Name the scientist who first said that current can cause magnetic field.
32.
Do magnetic monopoles exist?
33.
What is the smallest magnetic element?
34.
Give two areas in which magnetic techniques are used?
35.
Define magnetic field strength.
36.
What is the magnetic ore of iron called?
37.
What is the conclusion of Oersted’s experiment?
38.
What is the use of compass needle?
39.
What is netural point?
40.
Why can’t two magnetic field lines interact?
41.
State Right hand thumb rule.
42.
What are the factors affecting the strength of magnetic field at a point due to a straight conductor
carrying current?
43.
What is the nature of magnetic field produced due to a loop (circular) carrying current?
44.
When a coil carries current in anti-clockwise direction what pole does it create?
45.
Does a circular coil carrying current act as a dipole?
46.
What is solenoid?
47.
Give the basic laws of magnetism.
48.
Give name of two materials which permanent magnets are made.
49.
What is the nature of material used for making permanent magnets?
50.
What is an electro-magnet?
51.
What does the tangent at any point on magnetic field lines indicates?
52.
Can two magnetic field lines intersect?
53.
Give two devices using permanent magnets.
54.
What will happen when a current carrying conductor is placed in a perpendicular magnetic field?
55.
What is the significance of Flemings L. H. rule?
56.
What is Allen belt?
57.
What is the constituent of Van Allen belt?
58.
Nam two particle accelerators.
59.
Give the relation for force experienced by a moving charge entering a perpendicular magnetic
field.
60.
Name the energy transformation taking place in an electric motor.
61.
What is the principal behind the working of a motor.
62.
What is the meaning of E. M. I.?
63.
Define magnetic flux.
64.
What will happen when a magnet is taken towards a circular coil?
65.
What is the role of slip rings in an AC generator?
66.
What is the frequency of AC in India?
67.
What type of connection is used in electric circuits at home?
68.
Name the commercial unit for electrical energy.
69.
What is a fuse wire?
70.
Give two character essential for a fuse wire.
71.
Name the parameter that determines the strength of safe current that can be drawn.
72.
Name the composition of fuse wire.
73.
What is true equator?
74.
What is magnetic meridian?
75.
Define geographic meridian.
76.
Define geographic of dip.
77.
Write the relation connecting dip with horizontal and vertical components.
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CONTACT FOR MATHEMATICS GROUP/HOME COACHING FOR CLASS 11TH 12TH BBA,BCA,
DIPLOMA CPT CAT SSC AND OTHER EXAMS Also home tutors for other subjects in DELHI AND OTHER MAJOR CITIES
EMAIL:8 [email protected] web site www.badhaneducation.in
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CONTACT FOR COACHING MATHEMATICS FOR 11TH 12TH NDA DIPLOMA SSC CAT SAT CPT
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MAGNETIC EFFECTS OF ELECTRIC CURRENT
78.
Name the three components of earth’s field.
79.
Define declination.
80.
What is the angle of dip if the horizontal and vertical components are equal?
81.
What is the angle of dip at poles?
82.
What is the principal behind the working of a transformer?
83.
Does the transformer obey the law of conservation of energy?
84.
Will a transformer work with direct current?
85.
Why does a transformer not work in DC?
86.
What is the angular separation between magnetic and geographic axis?
87.
Which of the two requires a thin fuse wire to draw 5A or 15A?
88.
Give one disadvantage of using series connection at home.
89.
What are the constituents of Alnico?
90.
State Fleming’s R. H. rule.
91.
When do we apply Fleming’s (i) Left-hand (ii) Right-hand rule?
92.
Name two circumstances that make the fuse to burn.
93.
What is the relation for magnetic field at the center of a circular coil of radius r?
2 Marks Questions
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6.
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(ii)
(iii)
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13.
Define angle of dip. Write the relation connecting angle of dip and horizontal component of
earth’s magnetic field at a place?
Define S. I. unit of magnetic field. Under what condition does a moving charge experience (i)
Maximum force (ii) Minimum force?
Calculate the current drawn by the primary of transformer, which steps down 200 V to 20 V to
operate a device of resistance 20. Assume the efficiency of the transformer to be 80%.
How does the angle of dip vary as one moves from the equator towards the North pole? If the
horizontal component of earth’s magnetic field at a place where the angle of dip is 60° is 0.4 × 10–4
Tesla, calculate the vertical component and the resultant magnetic field of earth at that point.
State Faraday’s law of electromagnetic induction. Express it mathematically.
Define Netural point. Locate the position of netural points when a small bar magnet is placed with
its North pole (i) towards North of the earth and (ii) towards South of the earth.
Name the elements of earth’s magnetic field at a place. Explain their meaning.
Define angle of dip at a place. What is the angle of dip on the equator?
What are the energy losses in a transformer? How can they be minimized?
State Faraday’s law of E. M. induction.
What is probable cause for earth’s magnetism?
Compare the magnetic field of a Bar magnet and a Solenoid.
The horizontal component of earth’s magnetic field is 0.2 gauss and total magnetic field is 0.4
gauss. Find angle of dip.
Horizontal and vertical components of earth’s field at a place are 0.22 and 0.38 gauss. Calculate
the angle of dip and the resultant intensity of earth’s field.
Write the basic differences between magnetic and electric field lines.
What is the function of earth wire? Why it is necessary to earth the metallic appliances?
A coil of copper wire is connected to a galvanometer. What would happen if a bar magnet is
pushed into the coil with North pole entering first?
pulled out the bar magnet?
held stationary inside the coil?
Define magnetic declination.
What are magnetic lines of force? Roughly trace the magnetic field lines for a bar magnet.
What is the force that a conductor d1, carrying a current I, experiences when placed in a magnetic
field B? What is the direction of force?
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DIPLOMA CPT CAT SSC AND OTHER EXAMS Also home tutors for other subjects in DELHI AND OTHER MAJOR CITIES
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MAGNETIC EFFECTS OF ELECTRIC CURRENT
21.
What is the significance of Oersted’s experiment?
22.
What is the basic magnetic element? What is the name given to their ends?
23.
Why do we call the edges of a magnet poles?
24.
Why do we call the poles-North pole and South pole?
25.
Give two characters of magnetic field lines.
26.
How can you find the direction and strength of magnetic field from the field lines?
27.
A wire carrying current is passing through a hole at the middle of a cardboard. Plot the magnetic
field lines.
28.
Draw a sketch of the iron filings as you spray them on a magnet.
29.
State and explain how Right hand thumb rule indicates magnetic field.
30.
Explain in short how you can magnetise a piece of iron.
31.
What are electro and permanent magnets? Give two uses of each.
32.
Does a charge experience force in a magnetic field? Write the relation for force experienced.
33.
Why does a charge at rest, not experience any force in a magnetic field?
34.
Stat Fleming’s Left hand rule. What is the direction of force experienced?
35.
What is Van Allen radiation belt? What is the cause for it?
36.
What is the principal of and electric motor?
37.
Define Magnetic flux. Write its S. I. unit.
38.
When magnetic flux varies in a region, what happens?
39.
What is a couple? Why does a coil in a magnetic field rotate?
40.
Explain how a moving magnet produces current.
41.
A closed loop with a battery and a key is kept close to a loop with a galvanometer. What is the
change noticed in the coil?
42.
A steady current flows through a coil. What is the current flowing in a coil nearby? Give reason.
43.
State Fleming’s Right hand rule. How is it different from Left hand rule?
44.
Write the energy transformation in (i) AC generator (ii) Electric motor.
45.
How can we make an AC generator to produce DC?
46.
In house electric supply (i) what type of connection s used? (ii) What is the frequency of AC used?
47.
What is an electric fuse? Name the material used for making fuse. What all characters does it
have?
48.
What is the significance of the fuse wire?
49.
Define: Over-loading, short circuiting.
50.
What capacity of fuse wire is to be used for? (i) Bulb (ii) Geyser? Give reason.
51.
Define magnetic meridian, and geographic meridian.
52.
What are the components of earth’s magnetic field?
53.
Define angle of dip. Write its value at poles and equator.
54.
What is the cause for earth’s magnetic field?
55.
What is solenoid? Does it behave like a magnet?
56.
What is a transformer? What is the basic principal behind its working?
57.
What does a step-up and step-down transformer do? Does it violate law of conservation of energy?
58.
Define magnetic field strength. Write the S. I. unit.
59.
Give the characteristic of magnetic field due to a circular coil carrying current.
60.
Sketch the potential developed in an AC generator and DC generator.
61.
Who fist detected the presence of magnetic field in earth? Does the axis of the magnet and axis of
earth differ? How much?
62.
Define angle of dip. How is it related to the horizontal and vertical components?
63.
If the horizontal components is half the vertical component, find the angle of dip writing the
relation connecting them.
64.
How does the transformer, step-up or step-down, confirm to the law of conservation of energy?
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3 Marks Questions
CONTACT FOR MATHEMATICS GROUP/HOME COACHING FOR CLASS 11TH 12TH BBA,BCA,
DIPLOMA CPT CAT SSC AND OTHER EXAMS Also home tutors for other subjects in DELHI AND OTHER MAJOR CITIES
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BADHANEDUCATION D96 MUNIRKA VILLAGE NEW DELHI 110067 & VIKAS PURI NEW DELHI
CONTACT FOR COACHING MATHEMATICS FOR 11TH 12TH NDA DIPLOMA SSC CAT SAT CPT
CONTACT FOR ADMISSION GUIDANCE B.TECH BBA BCA, MCA MBA DIPLOMA AND OTHER COURSES 09810144315
MAGNETIC EFFECTS OF ELECTRIC CURRENT
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5 Marks question
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What is the relation for force experienced by a current carrying straight conductor placed in a
magnetic field. Under what condition is this force maximum?
Name the elements of earth’s magnetic field. Explain their meaning with a diagram.
Define the term magnetic declination and dip angle. Value of dip at a place in South India is 18°.
Will it be made or less in England?
(i) What are magnetic field lines?
(ii) Write two of their characteristics.
How can you draw magnetic field lines? Explain
Explain how Oersted explained the formation of magnetic field in its surrounding?
What are magnetic poles? How can you identify them?
How can we demonstrate the formation of magnetic field surrounding a magnet?
How can we magnatise a material? Give the character of magnetic materials used.
Does a current carrying conductor experience a force when placed in a magnetic field? Give two
applications of this.
Why does a rectangular coil carrying current rotate in a magnetic field?
What is electromagnetic induction? Write the rule that is used to find the direction of induced
current.
Explain how the movement of a magnet towards or away from a coil carrying a galvanometer
produces current.
Explain how Faraday explained the production of induced current.
State Fleming’s left and right hand rules. Express the areas of their application and give one
difference.
Why does a magnet kept stationary near a coil with a galvanometer not produce any deflection?
Explain/
Write the basic principal and working of an AC generator.
Draw a neat labeled diagram of an A generator.
Write the use of (i) Slip rings, (ii) Brushes and (iii) Armature in an AC generator.
What is a commutator? How does it being direct current. Show the output potential of an AC and
DC generator.
(i) Why do we prefer a parallel connection at home?
(ii) How does the earth sire help us to save various electrical appliances?
What is electric fuse? Name two materials used to make fuse wire. How does the variation in (i)
length and (ii) thickness of fuse wire affect the current drawn?
(i) Define the three components of earth’s field.
(ii) Write the relation between dip and horizontal component.
What is declination? How does it vary from place to place on the surface of earth?
What is Overloading? Why does a fuse wire melt on overloading?
Why does short circuit lead to the fuse wire burning?
Sketch the declination, dip at a place on earth’s surface (using meridian).
Draw a labeled diagram of an AC generator. Write the principal on which it works.
Explain with the help of a labeled diagram, the principal, construction and working of an AC
generator.
Explain principal, construction and working of and AC generator. How can it be modified to a DC
generator?
(i) Is earth a magnet? Give one cause for the same.
(ii) What are the components of earth’s magnetic field?
(iii) Relate dip with horizontal and vertical components of field.
CONTACT FOR MATHEMATICS GROUP/HOME COACHING FOR CLASS 11TH 12TH BBA,BCA,
DIPLOMA CPT CAT SSC AND OTHER EXAMS Also home tutors for other subjects in DELHI AND OTHER MAJOR CITIES
EMAIL:11 [email protected] web site www.badhaneducation.in
BADHANEDUCATION D96 MUNIRKA VILLAGE NEW DELHI 110067 & VIKAS PURI NEW DELHI
CONTACT FOR COACHING MATHEMATICS FOR 11TH 12TH NDA DIPLOMA SSC CAT SAT CPT
CONTACT FOR ADMISSION GUIDANCE B.TECH BBA BCA, MCA MBA DIPLOMA AND OTHER COURSES 09810144315
MAGNETIC EFFECTS OF ELECTRIC CURRENT
5.
Explain with a neat diagram, the principal, construction and working of an AC generator.
6.
What are magnetic field lines? How will your draw them? Write their characters.
7.
Explain with a neat diagram, the working of an electric motor.
8.
Show a domestic electric circuit with fuse, a bulb and a geyser from main electric line. Indicate
also the capacity of fuse used for geyser and the bulb.
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SELF EVALUATION TEST
Time allowed: 1 Hour
Max. Marks. 25
1.
Name the scientist who found that current carrying conductors produce magnetic field.
2.
List two characters of magnetic field lines.
3.
Why do we use fuse wire?
4.
State Fleming’s right hand rule. How is it different from left hand rule?
5.
How can you show the presence of a magnetic field surrounding a magnet?
6.
How do you magnetize a material? Name some materials used in the manufacture of permanent
magnets. Where do we use them?
7.
What will happen to a conductor placed in a magnetic field, used in the manufacture of
permanent it?
8.
Define dip and declination. How are they related to the horizontal field of earth?
9.
(i) What type of electric connection, we use in India.
(ii) Why do we use earth-wire?
10.
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(iii) What is overloading?
What are the factors affecting the magnetic field produced by a current carrying conductor?
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Write the magnetic field due to infinity long current carrying conductor.
Explain the principal construction and working of an AC generator, showing the output.
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CONTACT FOR MATHEMATICS GROUP/HOME COACHING FOR CLASS 11TH 12TH BBA,BCA,
DIPLOMA CPT CAT SSC AND OTHER EXAMS Also home tutors for other subjects in DELHI AND OTHER MAJOR CITIES
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