This set of Basic Electrical Engineering Question Paper focuses on “Current and Voltage in an Inductive Circuit”.

1. Inductor does not allow sudden changes in?

a) Voltage

b) Current

c) Resistance

d) Inductance

View Answer

Explanation: The inductor does not allow sudden changes in current because if current changes in the inductor occur in zero time, the voltage becomes zero which is not possible.

2. In case of Inductive circuit, Frequency is ______________ to the current.

a) Directly proportional

b) Inversely proportional

c) Unrelated

d) Much greater than

View Answer

Explanation: Inductance is inversely proportional to current since, as the inductance increases, current decreases.

3. If the resistance in a circuit is 2 ohm and the inductive resistance is 20 ohm, calculate the power factor.

a) 10

b) 20

c) 30

d) 40

View Answer

Explanation: We know that:

cos(phi)=R/XL

From the given question, we find that the power factor is 10.

4. If the power factor is 10 and the resistance is 2 ohm, calculate the inductive reactance.

a) 10 ohm

b) 20 ohm

c) 30 ohm

d) 40 ohm

View Answer

Explanation: We know that:

cos(phi)=R/XL

From the given question, we find that the inductive reactance is 20 ohm.

5. An induced emf is said to be ___________

a) Inductive

b) Capacitive

c) Resistive

d) Cannot be determined

View Answer

Explanation: Any circuit in which a change of current is accompanied by a change of flux, and therefore by an induced emf, is said to be inductive.

6. In a pure inductive circuit, the power factor is?

a) Maximum

b) Minimum

c) 0

d) Infinity

View Answer

Explanation: In a pure inductive circuit, current is lagging by 90 degrees from the voltage. The power factor is the cosine of the angle in between the voltage and the current. If the angle between the voltage and current is 90, then cos90=0. Hence, the power factor is zero.

7. Among the following, which is the right formula for inductance?

a) L=emf*t/I

b) L=emf/t*I

c) L=emf*I/t

d) L=emf*t*I

View Answer

Explanation: The average emf induced is proportional to the current per unit time, the constant of proportionality being L. Hence emf=LI/t. Making L the subject of the formula, we get: L=emf*t/I.

8. Among the following, which is the right formula for inductance?

a) L=NΦ/t

b) L=NΦt

c) L=N/Φt

d) L=NΦ^{2t}

View Answer

Explanation: The average emf induced in a coil is L=NΦ/t.

9. If the current in a coil having a constant inductance of L henrys grows at a uniform rate, what is the value of the average current?

a) I

b) I/2

c) I/4

d) 0

View Answer

Explanation: The average current is the average of the current which flows in the inductor. Hence it is I/2.

10. Find the average current in an inductor if the total current in the inductor is 30A.

a) 10A

b) 26A

c) 15A

d) 5A

View Answer

Explanation: Average current= I/2.

Substituting the value of I from the equation, average current= 13A.

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