Three large parallel plates are arranged as shown. The middle plate initially carries charge Q and the right plate 2Q. The outer plates are connected by key K. How much charge flows through K when it is closed?
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Question

Three large parallel plates are arranged as shown. The middle plate initially carries charge Q and the right plate 2Q. The outer plates are connected by key K. How much charge flows through K when it is closed?

Options

G1 Physics · Accepted Answer

Use charge conservation and equal-potential condition of the two outer plates after the key closes. Solving surface charges gives transferred charge 5Q/6. Correct answer: A.