The figure given below shows an LCR series circuit with two switches S 1 and S 2 . When switch S 1 is closed keeping S 2 open, the phase difference φ between current and source voltage is 30 ° and phase difference is 60 ° when S 2 is closed keeping S 1 open. The value of (3L 1 - L 2) is H.

Physics · Alternating Current

JEE Main 2026 — 2 April, Evening Shift — Question 15

The figure given below shows an LCR series circuit with two switches $S_1$ and $S_2$ . When switch $S_1$ is closed keeping $S_2$ open, the phase difference $\phi$ between current and source voltage is $30^\circ$ and phase difference is $60^\circ$ when $S_2$ is closed keeping $S_1$ open. The value of $(3L_1 - L_2)$ is H.

Option A:
$\frac{9}{2}$
Option B:
$\frac{2}{9}$
Correct
Option C:
$\frac{1}{3}$
Option D:
3

Answer: B

Step-by-step solution

From phasor: $\frac{\omega L_1 - 1/\omega C}{R}=\tan30^\circ$ , $\frac{\omega L_2 - 1/\omega C}{R}=\tan60^\circ$ solving yields $3L_1-L_2 = \frac{2}{9}$

Answer key and solution verified before publishing.

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Exam: JEE Main 2026
Paper: 2 April, Evening Shift
Subject: Physics
Chapter: Alternating Current
Topic: Series L-R, R-C, L-C Circuits with AC Source