Electromagnetic Induction MCQs Quiz Multiple Choice Questions & Answers

1. Whenever the magnetic flux linked with an electric circuit changes, an emf is induced in the circuit. This is called

1. electromagnetic induction
2. lenz's law
3. hysteresis loss
4. kirchhoff's laws

2. In electromagnetic induction, the induced charge is independent of

1. change of flux
2. time.
3. resistance of the coil
4. None of these

3. An induced e.m.f. is produced when a magnet is plunged into a coil. The strength of the induced e.m.f. is independent of

1. the strength of the magnet
2. number of turns of coil
3. the resistivity of the wire of the coil
4. speed with which the magnet is moved

4. According to Faraday's law of electromagnetic induction

1. electric field is produced by time varying magnetic flux.
2. magnetic field is produced by time varying electric flux.
3. magnetic field is associated with a moving charge.
4. None of these.

5. A moving conductor coil produces an induced e.m.f. This isin accordance with

1. Lenz's law
2. Faraday's law
3. Coulomb's law

6. A coil of insulated wire is connected to a battery. If it is taken to galvanometer, its pointer is deflected, because

1. the induced current is produced
2. the coil acts like a magnet
3. the number of turns in the coil of the galvanometer are changed
4. None of these

7. The polarity of induced emf is given by

1. Ampere's circuital law
2. Biot-Savart law
3. Lenz's law
4. Fleming's right hand rule

8. The self inductance of a coil is a measure of

1. electrical inertia
2. electrical friction
3. induced e.m.f.
4. induced current

9. The coils in resistance boxes are made from doubled insulated wire to nullify the effect of

1. heating
2. magnetism
3. pressure
4. self induced e.m.f.

10. Two pure inductors each of self inductance L are connected in series, the net inductance is

1. L
2. 2 L
3. L/2
4. L/4

11. Lenz's law is a consequence of the law of conservation of

1. charge
2. mass
3. energy
4. momentum

12. A magnet is moved towards a coil (i) quickly (ii) slowly, then the induced e.m.f. is

1. larger in case (i)
2. smaller in case (i)
3. equal to both the cases
4. larger or smaller depending upon the radius of the coil

13. The laws of electromagnetic induction have been used in the construction of a

1. galvanometer
2. voltmeter
3. electric motor
4. generator

14. Two coils are placed closed to each other. The mutual inductance of the pair of coils depends upon

1. the rate at which currents are changing in the two coils.
2. relative position and orientation of two coils.
3. the material of the wires of the coils.
4. the currents in the two coils.

15. Two identical coaxial circular loops carry a current i each circulating in the same direction. If the loops approach each other, you will observe that the current in

1. each increases
2. each decreases
3. each remains the same
4. one increases whereas that in the other decreases

16. When current in a coil changes from 5 A to 2 A in 0.1 s, average voltage of 50 V is produced. The self-inductance of the coil is

1. 1.67 H
2. 6 H
3. 3 H
4. 0.67 H

17. The self inductance associated with a coil is independent of

1. current
2. induced voltage
3. time
4. resistance of a coil

18. A coil having 500 sq. loops of side 10 cm is placed normal to magnetic flux which increases at a rate of 1 T/s. The induced emf is

1. 0.1 V
2. 0.5 V
3. 1 V
4. 5 V

19. A coil of 100 turns carries a current of 5 mA and creates a magnetic flux of 10-5 weber. The inductance is

1. 0.2 mH
2. 2.0 mH
3. 0.02 mH
4. 0.002 H

20. The north pole of a long bar magnet was pushed slowly into a short solenoid connected to a short galvanometer. The magnet was held stationary for a few seconds with the north pole in the middle of the solenoid and then withdrawn rapidly. The maximum deflection of the galvanometer was observed when the magnet was

1. moving towards the solenoid
2. moving into the solenoid
3. at rest inside the solenoid
4. moving out of the solenoid

21. In a coil of self-induction 5 H, the rate of change of current is 2 As-1. Then emf induced in the coil is

1. 10 V
2. -10 V
3. 5 V
4. -5 V

22. Why is the core of a transformer laminated?

1. To prevent eddy currents
2. To prevent mutual induction
3. To prevent self induction
4. None of these.

23. Two identical coaxial coils P and Q carrying equal amount of current in the same direction are brought nearer. The current in

1. P increases while in Q decreases
2. Q increases while in P decreases
3. both P and Q increases
4. both P and Q decreases

24. Faraday's laws are consequence of the conservation of

1. charge
2. energy
3. magnetic field
4. both b and c

25. Direction of current induced in a wire moving in a magnetic field is found using

1. Fleming's left hand rule
2. Fleming's right hand rule
3. Ampere's rule
4. Right hand clasp rule

26. Which of the following statements is not correct?

1. Whenever the amount of magnetic flux linked with a circuit changes, an emf is induced in circuit.
2. The induced emf lasts so long as the change in magnetic flux continues.
3. The direction of induced emf is given by Lenz's law.
4. Lenz's law is a consequence of the law of conservation of momentum.

27. Lenz's law is a consequence of the law of conservation of

1. charge
2. energy
3. induced emf
4. induced current

28. A solenoid is connected to a battery so that a steady current flows through it. If an iron core is inserted into the solenoid, the current will

1. increase
2. decrease
3. remain same
4. first increase then decrease

29. There is a uniform magnetic field directed perpendicular and into the plane of the paper. An irregular shaped conducting loop is slowly changing into a circular loop in the plane of the paper. Then

1. current is induced in the loop in the anti-clockwise direction.
2. current is induced in the loop in the clockwise direction.
3. ac is induced in the loop.
4. no current is induced in the loop.

30. Which of the following does not use the application of eddy current?

1. Electric power meters
2. Induction furnace
3. LED lights
4. Magnetic brakes in trains

31. The north pole of a bar magnet is rapidly introduced into a solenoid at one end (say A). Which of the following statements correctly depicts the phenomenon taking place?

1. No induced emf is developed.
2. The end A of the solenoid behaves like a south pole.
3. The end A of the solenoid behaves like north pole.
4. The end A of the solenoid acquires positive potential.

32. A metal plate can be heated by

1. passing either a direct or alternating current through the plate.
2. placing in a time varying magnetic field.
3. placing in a space varying magnetic field, but does not vary with time.
4. both a and b are correct.

33. Identify the wrong statement.

1. Eddy currents are produced in a steady magnetic field.
2. Eddy currents can be minimized by using laminated core.
3. Induction furnace uses eddy current to produce heat.
4. Eddy current can be used to produce braking force in moving trains.

34. If number of turns in primary and secondary coils is increased to two times each, the mutual inductance

1. becomes 4 times
2. becomes 2 times
3. becomes A times
4. remains unchanged

35. When the rate of change of current is unity, the induced emf is equal to

1. thickness of coil
2. number of turns in coil
3. coefficient of self inductance
4. total flux linked with coil

36. Two inductors of inductance .L each are connected in series with opposite? magnetic fluxes. The resultant inductance is (Ignore mutual inductance)

1. zero
2. L
3. 2L
4. 3L

37. An e.m.f is produced in a coil, which is not connected to an external voltage source. This is not due to

1. the coil being in a time varying magnetic field.
2. the coil moving in a time varying magnetic field.
3. the coil moving in a constant magnetic field.
4. the coil is stationary in external spatially varying magnetic field, which does not change with time.

38. Eddy currents do not cause

1. damping
2. heating
3. sparking
4. loss of energy

39. A wire loop is rotated in a magnetic field such that the frequency of change of direction of the induced emf is

1. Six times per revolution
2. Four times per revolution
3. Twice per revolution
4. Once per revolution

40. Which of the following is the equivalent quantity of mass in electricity?

1. Current
2. Charge
3. Potential
4. Inductance

41. What is the unit of inductance?

1. Volt/ampere
2. Joule/ampere
3. Volt-ampere/sec
4. Volt-sec/ampere

42. What is the angle made by the plane of eddy currents with the plane of magnetic lines of force?

1. 0^o
2. 40^o
3. 90^o
4. 180^o