• # question_answer Two conducting rings P and Q of radius r and 3r move in opposite directions with velocities 2v and v, respectively on a conducting surface S. There is a uniform magnetic field of magnitude B perpendicular to the plane of the rings. The potential difference between the highest points of the two rings is A)  0                                 B)  2Brv    C)    6Brv    D)    10Brv

Solution :

${{V}_{A}}={{V}_{B}}=(B)(2v)(2r)$ $=4\,vr$                                                         (1) ${{V}_{C}}-{{V}_{D}}=(v)(v)(6r)=6\,Bvr$                      (2) Further ${{V}_{A}}={{V}_{D}},$from (1) and (2) ${{V}_{C}}-{{V}_{B}}=10\,Bvr$ Hence, the correction option is (d).

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