Q. A conducting rod of mass m and length l is placed over a smooth horizontal surface. A uniform magnetic field B is acting perpendicular to the rod. Charge q is suddenly passed through the rod and it acquires an initial velocity v on the surface, then q is equal to
(a) 2mv/Bl
(b) Bl/2mv
(c) mv/Bl
(d) Blv/2m
Ans: (c)