Inductive Circuit MCQ [Free PDF] – Objective Question Answer for Inductive Circuit Quiz

21. What happens to the inductance when the magnetic field strength decreases?

A. Increases
B. Decreases
C. Remains the same
D. Becomes zero

Answer: B

Inductance is directly proportional to the magnetic field strength in the coil, hence as the magnetic field strength decreases, inductance decreases.

 

23. What happens to the inductance when the current in the coil becomes double its original value?

A. Becomes half
B. Becomes four times
C. Becomes double
D. Remains same

Answer: D

ϕ is directly proportional to i.

Φ = Li

where

L is the constant of proportionality

So, when current gets double ϕ also becomes double keeping L same.

 

24. When the coil is wrapped around a ferromagnetic core, why is it difficult to determine the inductance?

A. The variation of flux is no longer proportional to the variation of current
B. Current does not exist in the coil
C. Flux does not exist in the coil
D. The value of current is too large to measure

Answer: A

When a coil is wrapped around a ferromagnetic core, it is difficult to determine the inductance because the variation of flux is no longer proportional to the variation of the current.

 

25. What happens to the inductance as the area of the cross section of the coil increases?

A. Increases
B. Decreases
C. Remains the same
D. Becomes zero

Answer: A

L = µ0 × N2 × A/l,

hence as the area of cross section A increases, the inductance also increases.

 

26. What happens to the inductance as the length of the magnetic circuit increases?

A. Increases
B. Decreases
C. Remains the same
D. Becomes zero

Answer: B

L = µ0 × N2 × A/l

hence as the length of the magnetic circuit l increases, the inductance decreases.

 

27. If the current changes from 20A to 10A in 5 seconds and the value of inductance is 1H, calculate the emf induced.

A. 8V
B. 6V
C. 4V
D. 2V

Answer: D

We know that:

emf = L(i2 − i1)/t

Substituting the values from the question we get emf = 2V.

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28. When a ferromagnetic core is inserted into an inductor, what happens to the flux linkage?

A. Increases
B. Decreases
C. Remains the same
D. Becomes zero

Answer: A

When a ferromagnetic core is introduced into an inductor, its flux increases because the number of magnetic field lines increases due to the introduction of magnetic field within the coil.

 

29. What happens to the current when a ferromagnetic material is introduced within an inductor?

A. Increases
B. Decreases
C. Remains the same
D. Becomes zero

Answer: C

When a ferromagnetic is introduced within an inductor, the current remains fairly constant. This is because the current does not depend on the magnetic field.

 

30. What is the relation between the flux and the magnetizing current when a ferromagnetic core is introduced within the inductor?

A. Directly proportional
B. Inversely proportional
C. Not proportional
D. Current is double of flux

Answer: C

When a ferromagnetic core is introduced within an inductor the flux changes rapidly, whereas the current changes at the same pace. Hence the two are not proportional.

 

31. What happens to the effective inductance when a ferromagnetic core is introduced?

A. Increases
B. Decreases
C. Remains the same
D. Becomes zero

Answer: A

The effective inductance increases when a ferromagnetic core is introduced within an inductor because of the flux increases. Inductance varies directly with the flux hence it increases.

 

32. A laminated steel ring is wound with 200 turns. When the magnetizing current varies between 5 and 7 A, the magnetic flux varies between 760 and 800 Wb. Calculate the inductance of the coil.

A. 40H
B. 4 H
C. 4000H
D. 0.004 H

Answer: C

From the formula of incremental inductance, we know that:

L = (Change in flux/Change in current) × Number of turns

Substituting the values from the given question, we get L = 4000 H.

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