Electromagnetic Induction Multiple Choice Questions and Answers for Practice

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 The magnet was held stationary for a few seconds with the north pole in the middle of the solenoid and then withdrawn rapidly.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