The resistance in the circuit on the right (R_{r}) is twice that of the circuit on the left (R), so the current (I_{r}) is half that of the left circuit (I). Power dissipated is equal to I_{r}^{2}*R_{r} , so the power dissipated in the right circuit is given by: P_{r} = (I/2)^{2}*(2R)

so P_{r} = I^{2}*R/2, but P = I^{2}*R so P_{r} = P/2

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