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. Become zero instantaneously
B. Grows monotonically
C. Decay monotonically
D. Oscillates instantaneously.

Answer

D

Explanation

When the capacitor is connected to a d.c. source and then disconnected, it charged and then it starts discharging through the inductor. An induced emf is produced in the circuit which opposes the growth of current in L. when the capacitor is fully discharged, the electric energy stored in the capacitor (i.e. 1/2 `q^(2)//C`) gets converted fully into magnetic field energy `(1//2 LI^2)`. As soon as the discharge of the capacitor is complete, current stops and the magnetic flux linked with L starts collapsing. therefore, an induced emf is again developed which starts recharging the capacitor in the opposite direction. when the recharging is completed, all magnetic energy stored in L appears as the electric energy between the plates of the capacitor. The entire process keeps on repeating and the energy taken from the cell keeps on oscillating between C and L. Hence the current in the circuit starts oscillating as soon as the d.c. source charging the capacitor is disconnected .