JEE Main · 2026 · 21 Jan 2026 · Shift 2 · Electromagnetic Induction

A capacitor C is first charged fully with potential difference of

V_{0}

and disconnected from the battery. The charged capacitor is connected across an inductor having inductance L . In t s

25%

of the initial energy in the capacitor is transferred to the inductor. The value of t is

____

Answer: (B)

Solution

In an LC oscillator, energy oscillates between capacitor and inductor. If 25% energy is transferred to inductor, 75% remains in capacitor. Since

U_{C} \propto Q^{2}

, we have

Q_{f}^{2} = 0.75 Q_{i}^{2}

, so

Q_{f} = \frac{3}{2} Q_{i}

. Charge varies as

Q (t) = Q_{i} cos (ω t)

where

ω = \frac{1}{L C}

. Setting

cos (ω t) = \frac{3}{2}

gives

ω t = \frac{π}{6}

, hence

t = \frac{π}{6 ω} = \frac{π L C}{6}

JEE Main · 2026 · 21 Jan 2026 · Shift 2 · Single correct option