An an ideal parallel `LC` circuit, the capacitor is charged by connecting it to a `DC` source which is then disconnected. The current in the circuit

Options

A. becomes zero instantaneously
B. oscillates instantaneously
C. grows monotonically
D. decays monotonically

Answer

B

Explanation

When capacitor is connected to a `DC` source and then disconnected, it gets charged and then it starts discharging through the inductor. When capacitor `C` is fully charged to `q_(0)`, the current in inductor `L` is zero at this instant an amount of energy `1/2 (q_(0)^(2))/C` is stored in electric field between the plates of the capcitor.
When circuit is closed, the capacitor begins to discharge through the inductor causing current to flow. The energy of electric field between the capacitor plates has transfered to magnetic field. By Lenz's law the dying magnetic field induces an emf in the inductance in the same direction as current. Hence `L-C` circuit sets up oscillations.