In an ideal LC (or lightly damped RLC) circuit, the charge on the capacitor and current in the inductor oscillate sinusoidally — this is simple harmonic oscillation. The differential equation for an LC circuit is \(L\frac{d^2q}{dt^2} + \frac{q}{C} = 0\), identical in form to the SHM equation \(\ddot{x} + \omega^2 x = 0\).