In the shown circuit, switch S is kept open for a long time and then closed. The charge that flows through the battery when S is closed is:
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Question

In the shown circuit, switch S is kept open for a long time and then closed. The charge that flows through the battery when S is closed is:

G1 Physics · Accepted Answer

Before closing, the two identical capacitors are effectively in series across E, so each carries charge CE/2. After closing, the switching changes the node connection and the final battery charge differs by CE/2. Hence the charge through the battery is CE/2. Correct answer: B.