Question

The reactive power demanded by a circuit element will be zero when the phase difference between the current passing through it and the voltage across it becomes equal to

• A. zero degree
• B. \( \pm 45 \) degrees
• C. \( \pm 90 \) degrees
• D. \( \pm 180 \) degrees

Hint:

Zero reactive power occurs when the voltage and current are in phase (i.e., \( \theta = 0^\circ \) or \( 180^\circ \)).

Answer 1

The Correct Option is A

Step 1: Understanding reactive power.
Reactive power \( Q \) is given by \( Q = V I \sin \theta \), where \( \theta \) is the phase difference between voltage and current.
Step 2: Condition for zero reactive power.
For reactive power to be zero, \( \sin \theta = 0 \), which occurs when \( \theta = 0^\circ \) or \( 180^\circ \).
Step 3: Conclusion.
Thus, the reactive power is zero when the phase difference is 0° or 180°, which corresponds to option (A).