Question

Two conducting rings P and Q of radii r and 2r rotate uniformly in opposite directions with centre of mass 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. zero
• B. 4 Bvr
• C. 8 Bvr
• D. 16 Bvr

Answer 1

The correct option is C 8 Bvr

The circuit can be redrawn as two rods in linear motion
$V_p+4Bvr=V_A$
$V_Q-4Bvr=V_B$
$V_A-V_B=8Bvr$