This document contains 23 multiple choice questions related to magnetic effects of electric current. The questions cover topics like magnetic field patterns around current carrying wires, electromagnetic induction, electric generators, motors, transformers and other electric devices. There are also questions about the right hand rule, Fleming's left hand rule and their applications to determine magnetic field directions.

1. Magnetic Effects of Electric
Current NCERT QUESTIONS

2. Question 1.
Which of the following correctly describes the magnetic force near a long straight wire?
(a) The field consists of straight lines perpendicular to the wire.
(b) The field consists of straight lines parallel to the wire.
(c) The field consists of radial lines originating from the wire.
(d) The field consists of concentric circles centred on the wire.
Question 2.
The phenomenon of electromagnetic induction is
(a) the process of charging a body.
(b) the process of generating magnetic field due to current passing through coil.
(c) the process of producing induced current in coil due to relative motion between a magnet and the coil.
(d) the process of rotating a coil of an electric motor.
Question 3.
The device used for producing electric current is called
(a) generator (b) galvanometer
(c) ammeter d) moto

3. Question 4.
The essential difference between AC generator and DC generator is that:
(a) AC generator has electromagnet while DC generator has permanent magnet.
(b) DC generator higher voltage.
(c) AC generates higher voltage
(d) Ac generator has slip rings while DC generator has commutator.
Question 5.
At the time of short circuit, the current in the circuit
(a) reduces substantially. (b) does not change.
(c) increases heavily. (d) vary continuously.
Question 6
State whether the following statements are true or false.
(a) An electric motor converts mechanical energy into electrical energy.
(b) An electric generator works on the principle of electromagnetic induction.
(c) Field at the centre of a long circular coil carrying current will be parallel.
(d) Wire with a green insulation is usually the live wire of an electric supply.

4. Question 6.
State whether the following statements are true of false.
(a) An electric motor converts mechanical energy into electrical energy.
(b) An electric generator works on the principle of electromagnetic induction.
(c) Field at the centre of a long circular coil carrying current will be parallel.
(d) Wire with a green insulation is usually the live wire of an electric supply.
Question 7.
List three methods of producing magnetic fields.
Question 8.
How does a solenoid behave like a magnet? Can you determine the north and south poles of a current carrying solenoid using a bar
magnet? Explain.
Solution
A solenoid behaves like a magnet when electric current passes through it. Such a solenoid is called electromagnet. One end of a
solenoid behaves as a north pole and the other end behaves as a south pole. We can use a bar magnet to determine the north and
south poles of a current carrying solenoid by using property of like poles to repel and unlike poles to attract each other. The end of
solenoid which attracts North Pole of a bar magnet is magnetic South Pole in a solenoid. The end which repels the north pole of bar
magnet is the magnetic north pole of solenoid.
Question 9.
When the force experienced by a current carrying conductor placed in magnetic is fielded largest?

5. Solution
when conductor is kept perpendicular to the direction of the magnetic field.
Question 10
.Imagine that you are sitting in a chamber with your back to one wall. An electron beam, moving horizontally from back wall
towards the front wall, is deflected by a strong magnetic field to your right side. What is the direction of magnetic field?
Solution
The direction of electron are from back wall towards front wall.So current will from front wall to back wall. The direction of the force
is towards right According to Fleming’s left hand rule, direction of magnetic field will be vertically downward.
Question 11
Draw a labelled diagram of an electric motor. Explain its principle and working.What is the function of a split ring in an electric
motor?
Question 12.
Name some devices in which electric motors are used.
Question 13.
A coil of insulated copper wire is connected to a galvanometer. What will happen if a bar magnet is (i) pushed into the coil, (ii)
withdrawn from inside the coil and (iii) held stationary inside the coil?
Solution
(i) The galvanometer shows a deflection, which means current is induced in the coil. Current is induced in the coil due to the relative
motion between coil and magnet.
(ii)The galvanometer shows a deflection in opposite direction, which means current is induced in opposite direction. In this case, the
direction of motion is in the opposite direction w r.t. coil.
(iii) There is no deflection in galvanometer as no current is induced in the coil. There is no relative motion between coil and current,
so on current will be induced in the coil.

6. Question 14.
Two circular coils A and B are placed close to each other. If the current in coil A to changed, will some current be induced in the
coil?
Give reason.
Solution
Yes, current will be induced in coil B. when the current in coil A is changed, the magnetic field around it changes. So, the changing,
magnetic field lines around coil B induce a current in coil B.
Question 15.
State the rule to determine the direction of a
(i) magnetic field produced around a straight conductor carrying current.
(ii) force experienced by a current carrying straight conductor placed in a magnetic field.
(iii) current induced in a coil due to its rotation in magnetic field.
Question 16
Explain the underlying principle and working of an electric generator by drawing labelled diagram. What is the function of brushes?
Question 17.
When does an electric short circuit occur?
Question 18.
What is the function of an earth wire? Why is it necessary to earth metallic appliances?

7. Solution
The main function of the earth wire is to conduct the leaking current from the electrical appliance to the ground . It is connected to
the outer metallic body of the appliance .
It is necessary to earth metallic appliances , as it protects the user from electric shocks by transferring the current to the earth
Question.19
Why does a compass needle get deflected when brought near a bar magnet?
Answer: When a compass needle is brought near a bar magnet, the compass needle experiences a deflection. This happens
because of interaction of magnetic fields of the compass needle and the bar magnet.
Question 20
Why don’t two magnetic lines of force intersect each other?
Answer: The direction of magnetic field lines is always from the north pole to the south pole. If the field lines would cross each other
then the direction of field line would change at the point of crossing which is practically impossible. Hence, two magnetic field lines
never intersect each other.
Question 21
Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right hand
rule to find out the direction of the magnetic field inside and outside the loop.
Answer: As the given figure shows; current is flowing clockwise through a circular loop. The direction of magnetic field around the
conductor can be known by using the right hand thumb rule. As the figure shows, the magnetic field would be towards the plane of
the paper when it is inside the loop. On the other hand, the magnetic field would be away from the paper when it is outside the loop.

8. Question 22: The magnetic field in a given region is uniform. Draw a diagram to represent it.
Answer
The magnetic field lines are uniform inside a current carrying long straight solenoid
Question 23
The magnetic field inside a long straight solenoid-carrying current
1. Is zero
2. Decreases as we move towards its end
3. Increases as we move towards its end
4. Is the same at all points
Question 23: Which of the following property of a proton can change while it moves freely in a magnetic field? (There may be more
than one correct answer.)(a) Mass (b) speed (c) velocity (d) momentum
Answer (c) velocity and (d) momentum
When a proton enters in a region of magnetic field, it experiences a magnetic force. The magnetic force, acting perpendicular to the
velocity of the particle, will cause circular motion. Hence, velocity and momentum of proton changes when it moves in a magnetic
field.

9. Question 24 In Activity 13.7 (page: 230), how do we think the displacement of rod AB will be affected if (i) current in rod AB is
increased: (ii) a stronger horseshoe magnet is used: and (iii) length of the rod AB is increased?
Answer: In this case, the displacement would vary directly as the strength of current, strength of magnetic field and length of the
conductor. Due to this, the displacement of conductor would be increased in all the three cases.
Question 25
A positively-charged particle (alpha-particle) projected towards west is deflected towards north by a magnetic field. The direction
of magnetic field is
1. Towards south 2. Towards east 3. Downward 4. Upward
Answer: This question can be solved by using Fleming’s Left Hand Rule. We know that the direction of current is opposite to the
direction of electron’s movement and hence it would be same as the direction of proton’s movement. So, the direction of current is
towards west. As per Fleming’s Left Hand Rule; the middle finger shows the direction of current, the forefinger shows the direction of
magnetic field and the thumb shows the direction of motion. Here, the deflection is towards north, i.e. in north westerly direction and
hence, the direction of magnetic field would be towards north, i.e. upward.
Question 26
An electric oven of 2 kW is operated in a domestic electric circuit (220 V) that has a current rating of 5 A. What results do you
expect? Explain.
Answer: The current drawn by the electric oven can be calculated using following formula: P = VI
Given; P = 2 kW = 2000 W and V = 220 V
Since, P = VI hence, I = P/V
Or, I = 2000 W ÷ 220 V = 9.09 A
Here, the oven is drawing 9.09 ampere of current from a 5 ampere source.Fuse element of the electric fuse will melt and break the
circuit.

10. Question 27 : What precaution should be taken to avoid the overloading of domestic electric circuits?
Answer
The precautions that should be taken to avoid the overloading of domestic circuits are as follows:
1. Too many appliances should not be connected to a single socket.
2. Too many appliances should not be used at the same time.
3. Faulty appliances should not be connected in the circuit.
4. Fuse or MCB of proper rating should be connected in the circuit.
Question 28
Why do we use fuse in series with any electrical appliance? Why should a fuse with defined rating not be replaced by one with
larger rating?
Answer
Fuses are always connected in series with the component(s) to be protected from overcurrent, so that when the fuse blows (opens)
it will open the entire circuit and stop current through the component(s).If a fuse is replaced by one with large ratings, the
appliances may get damaged while the protecting fuse does not burn off.
One Mark Questions
Question 1 How can you show that the magnetic field produced by a given electric current in the wire decreases as the distance
from the wire increases?
Question 2 What is the advantage of the third wire of earth connection in domestic appliances?
Question 3 How is the strength of the magnetic field at a point near a wire related to the strength of the electric current flowing in
the wire?
Question 4 On what effect of an electric current does an electromagnet work?
Question 5 Why is magnetism at the centre of a Bar magnet is Zero ?
Question 6 What is an armature? Why it is used?

11. Question 7 : If the number of circular current carrying coils are (1 ) doubled. (2) halved. Then how will the magnetic field produced by
it will change ?.
Question 8 : What is the usual current rating of the fuse wire in the line to feed (a) Fan . Light (b) Appliances of 2 Kwh or more
power.
MCQ’s
Question 1: Choose the incorrect statement from the following regarding magnetic lines of field
1. The direction of magnetic field at a point is taken to be the direction in which the north pole of a magnetic compass needle
points
2. Magnetic field lines are closed curves
3. If magnetic field lines are parallel and equidistant, they represent zero field strength
4. Relative strength of magnetic field is shown by the degree of closeness of the field lines
( Answer :3 )
Question 2 :A soft iron bar is inserted inside a current-carrying solenoid. The magnetic field inside the solenoid:
(a) Will decrease (b) Will increase (c) Will become zero (d) Will remain the same Answer : ( b)
Question 3 : In all the electrical appliances, the switches are put in the
a. live wire b. earth wire c. neutral wire d. all of above Answer ( c)
Question 4. A current carrying conductor is held in exactly vertical direction. In order to produce a clockwise magnetic field around
the conductor, the current should be passed in the conductor:
(a) From top to bottom (b) From left to right (c) From bottom to top (d) From right to left Answer ( a)

12. Question 5 : If the key in the arrangement (Figure 13.1) is taken out (the circuit is made open) and magnetic field lines are drawn over
the horizontal plane ABCD, the lines are
1. Concentric circles
2. Elliptical in shape
3. Straight lines parallel to each other
4. Concentric circles near the point O but of elliptical shapes as we go away from it
Answer: (a) Concentric circles
6. The force exerted on a current carrying wire placed in a magnetic field is zero when the angle between wire and the direction of
magnetic field is:
(a) 45o (b) 60o (c) 90o (d) 180o
Answer: (d) 180o
7. An induced emf is produced when a magnet is moved into a coil. The magnitude of induced emf does not depend on:
(a) The speed with which the magnet is moved b) The number of turns of the coil (c) The resistivity of the wire of the coil
(d) The strength of the magnet
Answer: (c) The resistivity of the wire of the coil

13. Question 8: For a current in a long straight solenoid N- and S-poles are created at the two ends. Among the following statements, the
incorrect statement is
1. The field lines inside the solenoid are in the form of straight lines which indicates that the magnetic field is the same at all
points inside the solenoid
2. The strong magnetic field produced inside the solenoid can be used to magnetise a piece of magnetic material like soft iron,
when placed inside the coil
3. The pattern of the magnetic field associated with the solenoid is different from the pattern of the magnetic field around a bar
magnet
4. The N- and S-poles exchange position when the direction of current through the solenoid is reversed
Answer: (c) The pattern of the magnetic field associated with the solenoid is different from the pattern of the magnetic field around a
bar magnet
Question 9 :- Commercial electric motors do not use
1. An electromagnet to rotate the armature
2. Effectively large number of turns of conducting wire in the current carrying coil
3. A permanent magnet to rotate the armature
4. A soft iron core on which the coil is wound
Answer: (c) A permanent magnet to rotate the armature (Since permanent magnet do not produce strong magnetic field it is not
used in commercial electric motors.)

14. Question: 9 - A constant current flows in a horizontal wire in the plane of the paper from east to west as shown in Figure 13.5. The
direction of magnetic field at a point will be North to South
1. Directly above the wire
2. Directly below the wire
3. At a point located in the plane of the paper, on the north side of the wire
4. At a point located in the plane of the paper, on the south side of the wire
Answer: (a) Directly above the wire
7. A positive charge is moving towards a person. The direction of magnetic field lines will be in
(a) Clockwise direction (b) Anticlockwise direction (c) Vertically upward direction (d) Vertically downward direction
Answer: (b) Anticlockwise direction
A positive charge is moving towards the observer. ... The positive charge moving towards you is a current flowing towards you.
So use the right hand grip, thumb pointing towards you, the direction of the current and your fingers point in a circle showing the
direction of the magnetic field.A positive charge is moving towards the observer. ... The positive charge moving towards you
is a current flowing towards you. So use the right hand grip, thumb pointing towards you, the direction of the current and your
fingers point in a circle showing the direction of the magnetic field.
. 8 An alpha particle is diverted towards west is deflected towards north by a field. The field is magnetic. What will be the
direction of field?
a. Towards south b. towards east c. downward d. upward
Answer:( d )

15. 9. A fuse should always be placed in the
(a) Live wire of the main circuit (b) Neutral wire of the main circuit (c) Earth wire of the main circuit (d) Bothe live and neutral wire of
the main circuit.
Answer: (a) Live wire of the main circuit (A fuse is always connected in the live wire of the circuit. Explain the reason. A fuse is a
circuit element made of highly resistance material such that melts when there is overloading in the circuit. It is always connected in
the live wire as to break the circuit preventing the connected devices from damage)
10. A coil of insulated copper wire is connected to a galvanometer forming a loop and a magnet is:
A: Held stationary B: Moved away along its axis C: Moved towards along its axis
There will be a induced current in:
(a) A only (b) A and B only (c) B and C only (d) A, B and C
Answer: (c) B and C only
Question: 11 :- A uniform magnetic field exists in the plane of paper pointing from left to right as shown in Figure 13.3. In the field an
electron and a proton move as shown. The electron and the proton experienc
1. Forces both pointing into the plane of paper
2. Forces both pointing out of the plane of paper
3. Forces pointing into the plane of paper and out of the plane of paper, respectively
4. Force pointing opposite and along the direction of the uniform magnetic field respectively
Answer : Forces both pointing into the plane of paper.

17. Assertion and Reasoning Question
The correct option (B)

18. 13. Which of the following diagrams correctly shows the magnetic field produced by a current- carrying wire?
a) A
(b) B
(c) C
(d) D
Answer: (d) D
14 . A current flows in a wire running between the S and N poles of a magnet lying horizontally as shown in the figure below:

19. 14 . A current flows in a wire running between the S and N poles of a magnet lying horizontally as shown in the figure below:
The force on the wire due to the magnet is directed:
(a) From N to S
(b) From S to N
(c) Vertically downwards
(d) Vertically upwards
Answer: (c) Vertically downwards
15.

20. Answer : i .The constant current flowing in the straight wire produces a constant magnetic field. Hence, no induced current is produced
in the loop.
ii. Since current in the straight wire is changing, hence, induced current will be produced in clockwise direction.