An LC circuit (inductor + capacitor, no resistance) oscillates: charge $q = q_0\cos(\omega t)$ where $\omega = 1/\sqrt{LC}$. Energy oscillates between the capacitor ($U_E = q^2/(2C)$) and inductor ($U_B = LI^2/2$). Total energy is conserved: $U = q_0^2/(2C) = LI_0^2/2$. Analogy with SHM: $q \leftrightarrow x$, $I \leftrightarrow v$, $L \leftrightarrow m$, $1/C \leftrightarrow k$. With resistance (LCR circuit): damped oscillations,$\omega = \sqrt{1/(LC) - R^2/(4L^2)}$. This is the electrical analog of a damped harmonic oscillator.$