Question

At $t=0$ , switch $S_1$ is closed and remains closed for a long time and $S_2$ remains open. Now $S_1$ is opened and $S_2$ is closed. Find out the charge on the capacitor long after that moment.

Answer 1

Just after the switch is closed the situation is like this


After a long time, $i=0$

Potential difference,

$V_B-V_A=V_D-V_A=-2E$

So, charge on the capacitor after long time,

$Q=C(2E-0)=2EC$

Hence, option (b) is the correct answer.