Q.

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 some time, S2 is released and then S3 is pressed. After some time            [2013]

1 The charge on the upper plate of C1 is 2CV0  
2 The charge on the upper plate of C1 is CV0  
3 The charge on the upper plate of C2 is 0  
4 The charge on the upper plate of C2 is -CV0  

Ans.

(2, 4)

When switch S1 is pressed, the capacitor C1 gets charged such that its upper plate acquires a positive charge +2CV0 and the lower plate -2CV0.

When switch S2 is pressed and S1 is released, As C1=C2, the charge gets distributed equally. The upper plates of C1 and C2 now take charge +CV0 each, and the lower plates -CV0 each.

When S2 is released and S3 is pressed, the charge on the upper plate of C1 is CV0 and the charge on the upper plate of C2 is -CV0.