Circuit analysis — UPSC CSE 1992 Physics PYQ

The total energy, U in oscillating L-C circuit is given by: U = U_B + U_E = \frac{1}{2} L i^2 + \frac{1}{2} \frac{q^2}{C} When the resistance of the circuit is zero From this show that it is an oscillatory circuit and find the time period.