Current in an alternating circuit is ahead of voltage by a phase difference of \( \displaystyle\frac{\pi}{3} \). The alternating circuit is
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → RC circuit
The current leads the voltage only when the circuit is capacitive, and the phase lead lies between \( 0 \) and \( \pi/2 \) only when a resistance is also present.
In a series RC circuit
\( \displaystyle \tan\phi = \frac{X_C}{R} \)
so \( \phi = \pi/3 \) needs \( X_C = \sqrt{3}\,R \), which is possible. Hence the circuit is an RC circuit.
Why the other options are incorrect
Option (2) LC circuit — Incorrect. In an LC circuit (no resistance) the phase difference is exactly \( \pi/2 \), with the current leading or lagging, never \( \pi/3 \).
Option (3) LR circuit — Incorrect. In an LR circuit the current lags behind the voltage.
Option (4) L circuit — Incorrect. In a pure inductor the current lags the voltage by \( \pi/2 \).
NCERT (2026-27):
Phasor-Diagram Solution – “… If \( X_C \gt X_L \), \( \phi \) is positive and the circuit is predominantly capacitive. Consequently, the current in the circuit leads the source voltage. If \( X_C \lt X_L \), \( \phi \) is negative and the circuit is predominantly inductive. Consequently, the current in the circuit lags the source voltage.”