A vertical ring of radius `r` and resistance on `R` falls vertically. It is in contact with two vertical rails which are joined at the top. The rails are without friction and resistance. There is a horizontal uniform, magnetic field of magnitude `B` perpendicular to the plane of the ring and the rails. When the speed of the ring is `v` , the current in the section `PQ` is

Options

A. (a) `0`
B. (b) `(2Brv)/(R )`
C. ( c) `(4Brv)/(R )`
D. (d) `(8Brv)/(R )`

Answer

D

Explanation

(d ) `I = (2Brv)/(R//2) = (4Brv)/(R )`
,
Current in the top horizontal `= 2I = (8Brv)/(R)`.