1.
The property of coil by which a counter e.m.f is induced in it. when the current through the coil changes is known as

A

Self-inductance

B

Mutual inductance

C

Series aiding inductance

D

Capacitance

Answer/ Hint

2.
As per faraday’s law of electromagnetic induction, an e.m.f is induced in a conductor whenever it

A

Lies perpendicular to magnetic flux

B

Lies in a magnetic line

C

Cuts magnetic flux

D

Moves parallel to the direction of the magnetic field

Answer/ Hint

3.
Which of the following circuit elements stores energy in the electromagnetic filed?

A

Inductance

B

Condenser

C

Variable resistor

D

Resistance

Answer/ Hint

4.
The inductance of a coil will increase under all the following conditions excepts

A

When more length for the same number of turns is provided

B

When the number of turns of the coil increase

C

When more area for each turn is provided

D

When permeability of the core increases

Answer/ Hint

5.
Higher the self-inductance of the coil

A

Lesser its Webber-turns

B

Lower the e.m.f induced

C

Greater the flux produced by it

D

Longer the delay in establishing steady current through it

Answer/ Hint

6.
In an iron cored coil the iron core is removed so that the coil becomes an air cored coil. The inductance of the coil will

A

Increase

B

Decrease

C

Remain same

D

Initially increase then decrease

Answer/ Hint

7.
An open coil has

A

Zero resistance and inductance

B

Infinite resistance and zero inductance

C

Infinite resistance and normal inductance

D

Zero resistance and high inductance

Answer/ Hint

8.
Both the number of turn and core length of an inductive coil are doubled. Its self-inductance will be

A

Unaffected

B

Doubled

C

Halved

D

Quadrupled

Answer/ Hint

9.
If current in a conductor increases then according to lenz’s law self-inductance voltage will

A

Aid the increasing current

B

Tends to decrease the amount of current

C

Produce current opposite to the increasing current

D

Aid the applied voltage

Answer/ Hint

10.
The direction of induced e.m.f can be found by

A

Laplace’s law

B

Lenz’s law

C

Fleming’s right hand rule

D

Kirchhoff’s voltage law

Answer/ Hint

11.
Air-core coils are practically free from

A

Hysteresis losses

B

Eddy current losses

C

Both (a) and (b)

D

None of the above

Answer/ Hint

12.
The magnitude of the induced e.m.f in a conductor depends upon

A

Permeability of the core

B

The number of their turns

C

Cross-sectional area of their common core

D

All of the above

Answer/ Hint

13.
Mutually inductance between two magnetically-coupled coils depends upon

A

Permeability of the core

B

The number of their turns

C

Cross-sectional area of their common core

D

All of the above

Answer/ Hint

14.
A laminated iron core has reduced eddy-current losses because

A

More wire can be used with less D.C resistance in coil

B

The laminations are insulated from each other

C

The magnetic flux is concentrated in the air gap of the core

D

The laminations are stacked vertically

Answer/ Hint

15.
The law that the induced e.m.f and current always oppose the cause producing them is due to

A

Faraday’s

B

Lenz

C

Newton

D

Coulomb

Answer/ Hint

16.
Which of the following is not a unit of inductance?

A

Hennery

B

Coulomb/volt ampere

C

Volt second/ampere

D

All of the above

Answer/ Hint

17.
In case of an inductance, current is proportional to

A

Voltage across the inductance

B

Magnetic field

C

Both (a) and (b)

D

Neither (a) nor (b)

Answer/ Hint

18.
Which of the following circuit elements will oppose the change in circuit current?

A

Capacitance

B

Inductance

C

Resistance

D

All of the above

Answer/ Hint

19.
For a purely inductive circuit which of the following is true?

A

Apparent power is zero

B

Relative power is zero

C

Actual power of the circuit is zero

D

Any capacitance even if present in the circuit will not be charged

Answer/ Hint

20.
Which of the following is unit of inductance?

A

Ohm

B

Henry

C

Ampere turns

D

Weber/meters

Answer/ Hint

21.
An e.m.f of 16 volts is induced in a coil of inductance 4H. the rate of change of current must be

A

64 A/s

B

32 A/s

C

16 A/s

D

4 A/s

Answer/ Hint

22.
The core of the coil has a length of 200 mm. the inductance coil of 6 mH. If the core length is doubled, all other quantities, remaining the same, the inductance will be

A

3 mH

B

12 mH

C

24 mH

D

48 mH

Answer/ Hint

23.
The self-inductance of two coils are 8 mH. If the co-efficient of coupling is 0.5, the mutual inductance of the coil is

A

4 mH

B

5 mH

C

6 mH

D

12 mH

Answer/ Hint

24.
Two coil have inductance of 8 mH and 18mH and co-efficient of coupling of 0.5. if the two coils are connected in series aiding, the total inductance will be

A

32 mH

B

38 mH

C

40 mH

D

48 mH

Answer/ Hint

25.
A 200 turn coil has an inductance of 12 mH. If the number of turns is increased to 400 turns, all other quantities ( area, length etc.) remaining the same, the inductance will be

A

6 mH

B

14 mH

C

24 mH

D

48 mH

Answer/ Hint

26.
Two coils have self-inductance of 10 h and 2 h, the mutual inductance being zero. If the two coils are connected in series, the total inductance will be

A

6 H

B

8 H

C

12 H

D

24 H

Answer/ Hint

27.
In case all the flux from the current in coil 1 links with coil 2, the co-efficient of coupling will be

A

2.0

B

1.0

C

0.5

D

Zero

Answer/ Hint

28.
The energy in joules stored in magnetic field of 0.15 h inductance with a 180 mA current will be

A

2.43

B

2.43 x 10 ^{-3}

C

2.43 x 10 ^{-6}

D

2.43 x 10 ^{-9}

Answer/ Hint

29.
A coil with negligible resistance has 50 V across it with 10 mA. The inductive reactance is

A

50 ohms

B

500 ohms

C

1000 ohms

D

5000 ohms

Answer/ Hint

30.
Lenz’s law is a consequence of the law of conversion of

A

Induced current

B

Charge

C

Energy

D

Induced e.m.f

Answer/ Hint

31.
The co-efficient of coupling between the air core coils depends upon

A

Self-inductance of two coils only

B

Mutual inductance of two coils only

C

Mutual inductance and self-inductance of two coils

D

None of the above

Answer/ Hint

32.
An average voltage of 10 v is induced in a250 turns solenoid as a result of a change in flux which occurs in 0.5 seconds. The total flux change is

A

20 Wb

B

2 Wb

C

0.2 Wb

D

0.02 Wb

Answer/ Hint

33.
A 500 turns solenoid develops an average induced voltage of 60 V. over what time interval must a flux change of 0.06 Wb occur to produce such a voltage?

A

0.01 s

B

0.1 s

C

0.5 s

D

5 s

Answer/ Hint

34.
Which of the following inductor will have the least eddy current losses?

A

Air core

B

Laminate iron core

C

Iron core

D

Powdered iron core

Answer/ Hint

35.
A coil induces 350 mV when the current changes at the rate of 1 A/s. the value of inductance is

A

3500 mH

B

350 mH

C

250 mH

D

150 mH

Answer/ Hint

36.
Two 300 µH coils in series without mutual coupling have a total inductance of

A

300 µH

B

600 µH

C

150 µH

D

75 µH

Answer/ Hint

37.
Current charging from 8 A to 12 a in on second induced 20 volts in a coil. The value of inductance is

A

5 mH

B

10 mH

C

5 H

D

10 H

Answer/ Hint

38.
Which circuit element will oppose the change in circuit current?

A

Resistance only

B

Inductance only

C

Capacitance only

D

Inductance and capacitance

Answer/ Hint

39.
A crack in the magnetic path of an inductor will result in

A

Unchanged inductance

B

Increased inductance

C

Zero inductance

D

Reduced inductance

Answer/ Hint

40.
A coil is wound on iron core which carries current I. the self-induced voltage in the coil is not affected by

A

Variation in coil current

B

Variation in voltage to the coil

C

Change of number of turns of coils

D

The resistance of magnetic path

Answer/ Hint

41.
Which of the following statements is correct?

A

The inductance of a coil carrying a constant DC current will change the current into pulses

B

The inductance of a coil carrying a constant DC current will increase the current

C

The inductance of a coil carrying a constant DC current will not affect the current

D

The inductance of a coil carrying a constant DC current will decrease the current

Answer/ Hint