Two conducting rings P and Q of radii r and 2 | vedclass

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(C) The motional electromotive force (emf) induced in a conducting ring of radius $R$ moving with velocity $v$ in a magnetic field $B$ is given by $E

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$8\, Bvr$

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(C) The motional electromotive force (emf) induced in a conducting ring of radius $R$ moving with velocity $v$ in a magnetic field $B$ is given by $E = B \cdot (2R) \cdot v$,where $2R$ is the effective length (diameter) of the ring moving perpendicular to the magnetic field.For ring $P$ with radius $r$ and velocity $2v$:$E_1 = B \cdot (2r) \cdot (2v) = 4Bvr$For ring $Q$ with radius $2r$ and velocity $v$:$E_2 = B \cdot (2 \cdot 2r) \cdot v = 4Bvr$Since the rings are rotating in opposite directions on the conducting surface $S$,the induced emfs act in series. The potential difference between the highest points of the two rings is the sum of the induced emfs:Potential Difference $= E_1 + E_2 = 4Bvr + 4Bvr = 8Bvr$.

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