1)

In the circuit shown in the figure, there are two parallel plate capacitors each of capacitance C, The switch S1 is pressed first to fully charge the capacitor C1  and then released. The switch S2 is then pressed to charge the capacitor C2, After sometime S2  is released and then S3   is pressed, after some time

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A) the charge on the upper plate of $C_{1}$ is $2CV_{0}$

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:

Option B,D

Explanation:

 After  pressing S1 charge on upper plate of C1  is +2CV0

 After pressing S2 this charge equally distributes in two capacitors. Therefore charge upper plates of both capacitors will be +CV0

 When S2 is released  and S3  is pressed charge on the upper plate of C1 remains unchanged (=+CV) but charge on upper plate of C2 is according to new battery (-CV0)