JEE Advanced 2013 · Paper 1 · Physics Q15

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PhysicsMultiple correct+4 / -1Question 15 of 60

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,

From left to right, four vertical branches share a common bottom wire: a battery 2V₀ (positive terminal up), capacitor C₁, capacitor C₂, and a battery V₀ (positive terminal up). Along the top wire, switch S₁ joins the 2V₀ battery to C₁, S₂ joins C₁ to C₂, and S₃ joins C₂ to the V₀ battery.

the charge on the upper plate of

C_1

2CV_0

the charge on the upper plate of

C_1

CV_0

the charge on the upper plate of

C_2

is 0.

the charge on the upper plate of

C_2

-CV_0

Answer and worked solution

Official answer: B, D

S₁: $C_1$ charges to $2V_0$ , upper plate $+2CV_0$ .

S₂: $C_1$ shares charge with the uncharged, equal $C_2$ : each has $CV_0$ (upper plates $+CV_0$ ).

S₃: $C_2$ is connected across the $V_0$ battery, whose positive terminal faces the lower side, so $C_2$ ends with upper plate $-CV_0$ . $C_1$ is isolated and keeps $+CV_0$ .

(B), (D)

Topics:Series and parallel combinations

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JEE Advanced 2013 · Paper 1, Physics question 15