Question

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.

Answer 1

The correct option is D oscillates instantaneously.

$\frac{q}{C}+L\frac{di}{dt}=0\Rightarrow \frac{d^{2}q}{d{t}^2}+\frac{q}{LC}=0$
which is equation of oscillatory motion.
$\Rightarrow q=q_{0}sin\omega t\Rightarrow \frac{dq}{dt}=i=q_0\omega cos\omega t$
where $\omega =\frac{1}{\sqrt{LC}}\Rightarrow$ current starts oscillation.