An oscillating circuit consists of a capacitor with capacitance a coil of inductance with negligible resistance, and a switch. With the switch disconnected, the capacitor was charged to a voltage and then at the moment the switch was closed. Find: (a) the current (t) in the circuit as a function of time; (b) the emf of self-inductance in the coil at the moments when the electric energy of the capacitor is equal to that of the current in the coil.