Two conducting rings of radii `r` and `2r` move in apposite directions with velocities `2 upsilon` and `upsilon` 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

Explanation

Replace the induced emfs in the rings by cells emfs
`e_(1) = B2r(2v) = 4 Brv`
`e_(2) = B(4r)v = 4Brv` The equilvalent circuit is

Hence the potential difference between the highest points of the two rings is `V_(2)-V_(1) = e_(1)+e_(2) = 8 Brv`