Engineering Questions with Answers - Multiple Choice Questions

Basic Electrical Engineering MCQ’s – Factors Determining the Inductance of a Coil

1 - Question

As the number of turns in the coil increases, what happens to the inductance of the coil?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero

View Answer

Answer: a
Explanation: Inductance is directly proportional to the square of the number of turns in the coil, hence as the number of turns increases, inductance also increases.




2 - Question

What happens to the inductance when the magnetic field strength decreases?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero

View Answer

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




3 - Question

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

View Answer

Answer: d
Explanation: ϕ is directly proportional to i.
Φ=Li where L is constant of proportionality
So, when current get double ϕ also becomes double keeping L same.




4 - Question

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

View Answer

Answer: a
Explanation: 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.




5 - Question

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

View Answer

Answer: a
Explanation: L=µ0*N2*A/l, hence as the area of cross section A increases, the inductance also increases.




6 - Question

What happens to the inductance as the length of the magnetic circuit increases?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero

View Answer

Answer: b
Explanation: L=µ0*N2*A/l, hence as the length of the magnetic circuit l increases, the inductance decreases.




7 - Question

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

View Answer

Answer: d
Explanation: We know that:
emf=L(i2-i1)/t
Substituting the values from the question we get emf=2V.

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