Question

In an oscillating $LC$ circuit, the total stores energy is $U$ and the maximum charge on the capacitor is $Q$ . When the charge on the capacitor is $Q/2$ , the energy stored in the inductor is :

• A. $U/2$
• B. $U/4$
• C. $\left(4/3\right)U$
• D. $3U/4$

Answer 1

The correct option is D $3U/4$

The total energy is given as,

$U=\frac{1}{2}\frac{Q^2}{C}$

The energy stored in the capacitor is given as,

$U_C=\frac{1}{2}\frac{{\left(Q/2\right)}^2}{C}$

$U_C=\frac{1}{4}U$

The energy stored in the inductor is given as,

$U_L=U-\frac{1}{4}U$

$U_L=\frac{3}{4}U$