Read the following statements carefully:
(A) The average power in an inductor over one complete cycle is zero.
(B) Self-inductance plays the role of inertia.
(C) Mutual inductance of a pair of coils depends on their separation as well as their relative orientation.
(D) The capacitive reactance increases with increase in frequency of applied a. c.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A), (B) and (C) only
(A) The average power in an inductor over one complete cycle is zero. — Correct. In an ideal inductor the current lags the voltage by \( 90^\circ \), so the average power \( V_{\mathrm{rms}} I_{\mathrm{rms}}\cos\phi \) is zero: the inductor takes energy from the source in one quarter cycle and returns it in the next.
(B) Self-inductance plays the role of inertia. — Correct. The induced emf opposes any change of current, just as inertia (mass) opposes any change of velocity.
(C) Mutual inductance of a pair of coils depends on their separation as well as their relative orientation. — Correct. The mutual inductance depends on how much of one coil's flux links the other, which changes with the distance and the angle between the coils.
(D) The capacitive reactance increases with increase in frequency of applied a. c. — Incorrect. The reactance decreases as the frequency rises.
\( \displaystyle X_C = \frac{1}{\omega C} = \frac{1}{2\pi f C} \)
Statements (A), (B) and (C) are correct, which is Option (1).
NCERT (2026-27):
AC Voltage Applied to an Inductor – “… Thus, the average power supplied to an inductor over one complete cycle is zero.”
Self-Inductance – “… Physically, the self-inductance plays the role of inertia.”
Mutual Inductance – “… It is also important to know that the mutual inductance of a pair of coils, solenoids, etc., depends on their separation as well as their relative orientation.”
AC Voltage Applied to a Capacitor – “… The capacitive reactance limits the amplitude of the current in a purely capacitive circuit in the same way as the resistance limits the current in a purely resistive circuit. But it is inversely proportional to the frequency and the capacitance.”