# Electromagnetics MCQ Questions Answers Electrical Engineering

## Electrical Engineering Electromagnetics MCQ Questions Answers

1) If the number of turns of a coil is increased two times, its inductance is ______

a) increased two times

b) decreased two times

c) decreased four times

d) increased four times

Option – d)

2) The mutual inductance between two coils is ……. Reluctance of magnetic path.

a) directly proportional to

b) inversely proportional to

c) independent of

d) none of the above

Option – b)

3) The e.m.f. induced in a …….. is the statically induced e.m.f.

a) d.c generator

b) transformer

c) d.c motor

d) none of the above

Option – b)

4) If the number of turns of a coil is increased, its inductance ………

a) remains the same

b) is increased

c) is decreased

d) none of the above

Option – b)

5) An iron-cored coil of 10 turns has reluctance of 100 AT/Wb. The inductance of the coil is ….

a) 1 H

b) 10 H

c) 0.1 H

d) 5 H

Option – a)

6) An 8-H choke is carrying a current of 500 mA. The energy stored in the magnetic field is……

a) 1 J

b) 0.5 J

c) 2 J

d) 4 J

Option – a)

7) The mutual inductance between two unity coupled coils of 9 H and 4 H is……….

a) 36 H

b) 13 H

c) 2.2 H

d) 6 H

Option – d)

8) If the frequency of flux is increased two times, the eddy current power loss is ……..

a) increased two times

b) decreased two times

c) increased four times

d) decreased four times

Option – c)

9) In the above question, what is the coefficient of coupling?

a) 0.5

b) 0.1

c) 0.26

d) 0.23

Option – d)

10) A 100 mH coil carries a current of 1 A. Energy stored in the magnetic field is

a) 1J

b) 0.05 J

c) 1.5 J

d) 2.5 J

Option – b)

11) In the above question, if the coils are connected in series – opposition, then total inductance is

a) 1 H

b) zero

c) 2 H

d) 4 H

Option – b)

12) If L and R denote inductance and resistance respectively, then dimensions of L/R are

a) M L2 T0

b) M2 L0 T

c) M0 L0 T

d) none of the above

Option – c)

13) Choke coil works on the principle of

a) mutual inductance

b) self-inductance

c) dynamically induced e.m.f.

d) none of the above

Option – c)

14) If time constant of RL series  circuit is 40ms, how long does it take to discharge?

a) 80 ms

b) 120 ms

c) 200 ms

d) 160 ms

Option – c)

15) A current through a coil of inductance 5 H is decreasing at the rate of 2 A/sec. The e.m.f. induced in the coil is

a) 2.5 V

b) – 2V

c) -10 V

d) 10 V

Option – d)

16) A coil of radius R has 400 turns and a self-inductance of 32 mH. What will be the inductance of a similar coil of 300 turns?

a) 18 mH

b) 64 mH

C) 8 mH

d) 16 mH

Option – a)

17) If N is the number of turns of the coil, the inductance varies as

a) N0

b) N

c) N-2

d) N2

Option – d)

18) When magnetic flux linking a conductor changes,

a) an e.m.f. is always induced

b) a current is always induced]

c) both e.m.f. and current are always induced

d) neither e.m.f. nor current is inducted

Option – a)

19) The cores in electrical machines are generally made of laminations to reduce

a) hysteresis loss

b) eddy current loss

c) copper loss

d) all above