1. In an ideal inductor connected to an alternating voltage source, the current lags the voltage by what phase angle?
A.
0°
B.
45°
C.
90°
D.
180°
Correct Answer:
90°
Explanation:
In an ideal inductor, the current lags the applied alternating voltage by 90°.
2. What is the average power consumed by an ideal inductor in an AC circuit?
A.
Zero
B.
VI
C.
V/I
D.
I²L
Correct Answer:
Zero
Explanation:
The voltage and current in an ideal inductor differ in phase by 90°, so the average power consumed is zero.
3. The opposition offered by an ideal inductor to alternating current is called:
A.
Resistance
B.
Inductive reactance
C.
Capacitive reactance
D.
Conductance
Correct Answer:
Inductive reactance
Explanation:
An ideal inductor opposes AC through its inductive reactance, given by X_L = 2πfL.
4. The inductive reactance of an ideal inductor increases when the frequency of the AC supply:
A.
Decreases
B.
Becomes zero
C.
Increases
D.
Remains unchanged
Correct Answer:
Increases
Explanation:
Inductive reactance is X_L = 2πfL, so it increases directly with frequency.
5. If the frequency of an AC supply connected to an ideal inductor is doubled, its inductive reactance becomes:
A.
Half
B.
Unchanged
C.
Double
D.
Four times
Correct Answer:
Double
Explanation:
Since X_L = 2πfL, doubling the frequency doubles the inductive reactance when inductance is constant.
6. For an ideal inductor connected to an AC source, the power factor is:
A.
Zero
B.
0.5
C.
1
D.
2
Correct Answer:
Zero
Explanation:
The phase difference between voltage and current is 90°, so the power factor cos 90° is zero.
7. In an ideal inductive AC circuit, electrical energy is mainly:
A.
Dissipated as heat
B.
Stored temporarily in the magnetic field
C.
Converted permanently into light
D.
Destroyed during each cycle
Correct Answer:
Stored temporarily in the magnetic field
Explanation:
An ideal inductor stores energy in its magnetic field and returns it to the source during another part of the cycle.
8. If the RMS voltage across an ideal inductor is V and its inductive reactance is X_L, the RMS current is:
A.
VX_L
B.
V + X_L
C.
V/X_L
D.
X_L/V
Correct Answer:
V/X_L
Explanation:
For an ideal inductive circuit, Ohm's law for AC gives I_RMS = V_RMS/X_L.
9. At zero frequency, the inductive reactance of an ideal inductor is:
A.
Zero
B.
Very large
C.
Equal to its resistance
D.
Equal to its capacitance
Correct Answer:
Zero
Explanation:
Using X_L = 2πfL, the inductive reactance becomes zero when the frequency is zero.
10. Which statement is correct for current in an ideal inductor connected to an AC source?
A.
Current is in phase with voltage
B.
Current leads voltage by 90°
C.
Current lags voltage by 90°
D.
Current is always zero
Correct Answer:
Current lags voltage by 90°
Explanation:
The defining phase relationship for an ideal inductor is that its current lags the applied voltage by 90°.
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