A conducting wire `xy` of lentgh `l` and mass `m` is sliding without friction on vertical conduction rails `ab` and `cd` as shown in figure. A uniform magnetic field `B` exists perpendicular to the plane of the rails, `x` moves with a constant velocity of

Options

A. `(mg R)/(Bl)`
B. `(mg R)/(B l^(2))`
C. `(mg R)/(B^(2)l^(2))`
D. `(mg R)/(B^(2) l)`

Answer

C

Explanation

`BIl = mg` or `B(Bvl)/(R )l = mg` or `v = (mg R)/(B^(2)l^(2))`