There are two concentric spherical shell of radii r and 2r. initially charge Q is given to the inner shell and both the switches are open

Question

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There are two concentric spherical shell of radii r and 2r. initially charge Q is given to the inner shell and both the switches are open. Page # 6 1.

If switch S1 is closed and then opened, charge on the outer shell will be (a) Q (b) Q/2 (c) –Q (d) –Q/2