question_answer

In 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:

A)  becomes zero instantaneously

B)  grows monotonically

C)  decays monotonically

D)  oscillates instantaneously

Correct Answer: D

Solution :

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 \[x\], the current   in inductor L is zero, at   this instant an amount of  energy \[{{i}_{1}},\]is stored in electric field between the plates of the capacitor. 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 transferred to     magnetic   field.   By Lenzs law the dying magnetic field induces an    emf    in    the   inductance in the same direction as current. Hence, LC circuit sets up oscillations.