This set of Basic Electrical Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Inductive and Non-Inductive Circuits”.

1. In case of Inductive circuit, Frequency is ______________ to the inductance.

a) Directly proportional

b) Inversely proportional

c) Unrelated

d) Much greater than

View Answer

Explanation: The formula for frequency in an inductive circuit is:

X

_{L}=2*π*f*L.

Therefore: f is inversely proportional to L.

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: The formula for frequency in an inductive circuit is:

X

_{L}=2*π*f*L => i=V/(2*π*f*L)

Therefore: f is inversely proportional to i.

3. In an inductive circuit, when the XL value increases, the circuit power factor?

a) Increases

b) Decreases

c) Remains the same

d) Becomes zero

View Answer

Explanation: tan ϕ = X

_{L}/R and Power factor=cos ϕ

As X

_{L}increases, tan ϕ increases, ϕ increases, cos ϕ decreases and hence power factor decreases.

4. If the current and voltage are 90 degrees out of phase, the power factor will be?

a) 0

b) Infinity

c) 1

d) Insufficient information provided

View Answer

Explanation: The power factor is the cosine of the angle between the voltage and the current. If the angle between the voltage and the current is 90, then cos90=0. Hence, the power factor is zero.

5. 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, the current is lagging by 90 degrees from the voltage. The power factor is the cosine of the angle 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.

6. If the power factor is 1/10 and the value of impedance is 20 ohm, calculate the resistance in the circuit.

a) 1 ohm

b) 2 ohm

c) 3 ohm

d) 4 ohm

View Answer

Explanation: We know that:

cos(ϕ)=R/Z

R=Z cos(ϕ) = 20/10 = 2 ohm.

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

a) 1/10

b) 1/20

c) 1/30

d) 1/40

View Answer

Explanation: We know that:

cos(ϕ)=R/Z = 2/20 = 1/10 ohm.

8. If tan ϕ = 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:

tan(ϕ)=XL/R

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

9. What is the unit for inductive reactance?

a) Henry

b) Ohm

c) Farad

d) Volts

View Answer

Explanation: Inductive reactance is nothing but the impedance. Impedance is the AC equivalent of resistance, hence the unit for inductive reactance is ohm.

10. 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.

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