Question

In the circuit shown in the figure, there are two parallel plate capacitors each of capacitance C. The switch $S_1 $ is pressed first to fully charge the capacitor $C_1 $ and then released. The switch $S_2 $ is then pressed to charge the capacitor $C_2. $ After some time, $S_2 $ is released and then $S_3 $ is pressed. After some time

• A. the charge on the upper plate of $C_1 \, is \, 2 \, CV_0 $
• B. the charge on the upper plate of $C_1 \, is \, CV_0 $
• C. the charge on the upper plate of $C_2 \, is \, 0 $
• D. the charge on the upper plate of $C_2 \, is \, -CV_0$

Answer 1

Answer: (B), (D)

After switch $S_{1}$ is closed, $C_{1}$ is charged by $2 CV _{0}$, when switch $S _{2}$ is closed, $C _{1}$ and $C _{2}$ both have upper plate charge $CV _{0}$.
When $S_{3}$ is closed, then upper plate of $C_{2}$ becomes charged by $- CV _{0}$ and lower plate by $+ CV _{0}$.