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

Explanation

Divide the ring into two semi-circular rings. These two rings can be repalced by a battery of emf `e=Bv` `(2r)` and resistance `R//2` .
`i=(e)/(R//4)=(4e)/(R)=(4.2Bvr)/(R)=(8Bvr)/(R)`
The direction of current is from `Q` to `P`