physics : class12 Pure Inductive Circuit : Wattless Current : Electromagnetic Induction and Alternating Currents MCQ Questions and Answers
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Pure Inductive Circuit
MCQ questions and answers.
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MCQ Questions
1. In a pure inductive AC circuit, the current lags behind the voltage by what phase angle?
A.
0°
B.
45°
C.
90°
D.
180°
Correct Answer:
90°
Explanation:
In a pure inductive circuit, the current lags behind the applied voltage by 90°.
2. What is the average power consumed in a pure inductive AC circuit?
A.
Zero
B.
VI
C.
V²I
D.
I²L
Correct Answer:
Zero
Explanation:
The phase difference between voltage and current is 90°, so the power factor is cos 90° = 0. Therefore, the average power is zero.
3. The opposition offered by a pure inductor to the flow of alternating current is called:
A.
Resistance
B.
Inductive reactance
C.
Capacitive reactance
D.
Conductance
Correct Answer:
Inductive reactance
Explanation:
A pure inductor opposes AC through its inductive reactance, given by X_L = 2πfL.
4. The inductive reactance of a pure inductor is given by:
A.
X_L = L/f
B.
X_L = 2πfL
C.
X_L = 1/(2πfL)
D.
X_L = 2πL/f
Correct Answer:
X_L = 2πfL
Explanation:
For a pure inductive circuit, inductive reactance is X_L = ωL = 2πfL.
5. If the frequency of AC through a pure inductor is increased, its inductive reactance:
A.
Decreases
B.
Remains unchanged
C.
Becomes zero
D.
Increases
Correct Answer:
Increases
Explanation:
Since X_L = 2πfL, inductive reactance increases directly with frequency.
6. In a pure inductive circuit, the current is expressed in relation to the voltage as:
A.
Current leads voltage by 90°
B.
Current is in phase with voltage
C.
Current lags voltage by 90°
D.
Current lags voltage by 180°
Correct Answer:
Current lags voltage by 90°
Explanation:
The voltage across a pure inductor leads the current by 90°, or equivalently, the current lags the voltage by 90°.
7. A pure inductive circuit is called a wattless circuit because:
A.
It has no current
B.
It consumes no average power
C.
Its voltage is zero
D.
Its inductance is zero
Correct Answer:
It consumes no average power
Explanation:
A pure inductor stores energy during part of the AC cycle and returns it during another part, resulting in zero average power consumption.
8. The power factor of a pure inductive circuit is:
A.
1
B.
1/2
C.
0
D.
√3/2
Correct Answer:
0
Explanation:
For a pure inductive circuit, the phase angle is 90°, so the power factor is cos 90° = 0.
9. For a pure inductor connected to an AC source, the current amplitude is determined by:
A.
I = V/X_L
B.
I = VX_L
C.
I = V + X_L
D.
I = X_L/V
Correct Answer:
I = V/X_L
Explanation:
In a pure inductive circuit, the current is given by the applied voltage divided by the inductive reactance: I = V/X_L.
10. When alternating current flows through a pure inductor, the inductor:
A.
Permanently consumes electrical energy
B.
Converts all electrical energy into heat
C.
Stores and returns energy periodically
D.
Produces no magnetic field
Correct Answer:
Stores and returns energy periodically
Explanation:
A pure inductor stores energy in its magnetic field and returns it to the source periodically, so it consumes no average power.
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