250+ TOP MCQs on Alternating Current in a Resistive & Inductive Circuit and Answers

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Basic Electrical Engineering Multiple Choice Questions on “Alternating Current in a Resistive & Inductive Circuit”.

1. Instantaneous voltage is the product of resistance and _____________ current in a resistive circuit.
A. Instantaneous
B. Average
C. RMS
D. Peak
Answer: A
Clarification: V=IR. So, V(t)=i(t)R
Instantaneous voltage is the product of resistance and instantaneous current in a resistive circuit.

2. Find the value of the instantaneous voltage if the resistance is 2 ohm and the instantaneous current in the circuit is 5A.
A. 5V
B. 2V
C. 10V
D. 2.5V
Answer: C
Clarification: We know that,
v=iR, substituting the given values from the question, we get v=10V.

3. The power for a purely resistive circuit is zero when?
A. Current is zero
B. Voltage is zero
C. Both current and voltage are zero
D. Either current or voltage is zero
Answer: D
Clarification: P=VIcosϕ Power in a circuit is the product of voltage, current and the cosine of the phase angle. Phase angle is 00 for purely resistive circuit so, P=VI. Hence if either voltage or current is zero, the power is zero.

4. The correct expression for the instantaneous current if instantaneous voltage is Vm(sint) in a resistive circuit is?
A. 1A
B. 2A
C. 3A
D. 4A
Answer: B
Clarification: We know that:V=Vm(sint)
Since i=V/R, we can write, i=Vm(sint)/R.

5. Calculate the resistance in the circuit if the rms voltage is 20V and the rms current is 2A.
A. 2 ohm
B. 5 ohm
C. 10 ohm
D. 20 ohm
Answer: C
Clarification: We know that:
R=V/I
Substituting the given values from the question, we get R=10 ohm.

6. The correct expression for the instantaneous current in a resistive circuit is?
A. i=Vm(sint)/R
B. i=Vm(cost)/R
C. i=V(sint)/R
D. i=V(cost)/R
Answer: A
Clarification: The instantaneous voltage can be written in terms of the maximum voltage in the following manner:
v=Vm(sint)
Since i=v/R, we can write, i=Vm(sint)/R.

7. Can ohm’s law be applied in an ac circuit?
A. Yes
B. No
C. Depends on the rms current
D. Depends on the rms voltage
Answer: A
Clarification: Ohm’s law can be applied in ac as well as dc circuits. It can be applied in ac circuits because the condition V=IR holds true even in ac circuits.

8. The correct expression for the instantaneous current if instantaneous voltage is Vm(sint) in an inductive circuit is?
A. i = Vm(sint)/XL
B. i = Vm(cost)/XL
C. i = -Vm(sint)/XL
D. i = -Vm(cost)/XL
Answer: D
Clarification: V=Vm*sint
I=V/XL = -Vm(cost)/XL (since current lags voltage by 900 in inductive circuit).