⇒AC Circuits

Correct Option is (C)

Maximum energy stored in a capacitor, ${\mathrm{E}}_1=\frac{{\mathrm{Q}}^2}{2\mathrm{C}}$

When energy is stored equally between the electric and magnetic fields, then energy in the capacitor is ${\mathrm{E}}_2=\frac{1}{2}{\mathrm{E}}_1$

If ${\mathrm{Q}}^{\prime }$ is the charge on the capacitor in this case, then ${\mathrm{E}}_2=\frac{{\mathrm{Q}}^{\prime 2}}{2\mathrm{C}}$.

$\begin{array}{rl}\therefore & \frac{{\mathrm{Q}}^{\prime 2}}{2\mathrm{C}}=\frac{1}{2}\frac{{\mathrm{Q}}^2}{2\mathrm{C}}\\ {\mathrm{Q}}^{\prime }& =\frac{\mathrm{Q}}{\sqrt{2}}.\end{array}$