Q. A metal wire of mass $m$ slides without friction on two rails placed at a distance $l$ aprt. The track lies in a uniform vertical magnetic field $\ B$. A constant current $i$ flows along the rails across the wire and brack down the other rail. The acceleration of the wire is
A) $\frac{B\ m\ i}{l}$
B) $mBi\ l$
C) $\frac{Bil}{m}$
D) $\frac{mi\ l}{B}$
Explanation
(c) Force on wire, $F = Bil\sin{90{^\circ}} = Bil.$ It acts perpendicular to the magnetic field as well as the length of wire. The acceleration in the wire
$a = \frac{F}{m} = \frac{Bil}{m}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.