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 $C_{1}is2C{V}_0$
  
• B. the charge on the upper plate of $C_{1}isC{V}_0$
  
• C. the charge on the upper plate of $C_{2}is0$
  
• D. the charge on the upper plate of $C_{2}is-C{V}_0$
  

Answer 1

Answer: (B), (D)

After switch $S_1$ is closed, $C_1$ is charged by $2C{V}_0$, when switch $S_2$ is closed, $C_1$ and $C_2$ both have upper plate charge $C{V}_0$.
When $S_3$ is closed, then upper plate of $C_2$ becomes charged by $-C{V}_0$ and lower plate by $+C{V}_0$.