Q 12-07-026NEETJEE MainMedium
In an LC circuit, the capacitor is initially charged. The energy is entirely magnetic after a time (period of oscillation $T$)
Answer: (A) $\dfrac{T}{4}$
Concept. The charge varies as $q_0\cos\omega t$; the energy is all magnetic when $q = 0$.
Step 1. First zero of $q$. $\omega t = \dfrac{\pi}{2}$, i.e. $t = \dfrac{T}{4}$.
Answer. $\dfrac{T}{4}$ (Option A).
Solution by Sreeraj P, M.Sc Physics