A wire of mass `m` and length `l` can slide freely on a pair of fixed, smooth.vertical rails (figure).A magnetic field `B` exists in the region in the direction perpendicular to the plane of the rails.The rails are connected at the top end by an initially unchanged capacitor of capacitance `C`.Find the velocity of the wire at any time `(t)` after released.Neglecting any electric resistance.(initial velocity of wire is zero)

Answer

B, C

Explanation

acceleration `a=(mg-ilB)/m`...(i) here `i=(dq)/(dt)=d/(dt) (cepsilon)=C(depsilon)/(dt)`
`i=Cd/(dt)(BVl)=CB l (dq)/(dt)`
`i=Cbla` ..(ii)
from eq.(i) and (ii)
`ma=mg-(CBla)lB`
`[m+CB^(2)l^(2)]a=mg`
`a=(mg)/(m+CB^(2)l^(2))v=0+at=("mgt")/(m+CB^(2)l^(2))`