Q 12-06-016NEETJEE MainMedium
A conducting rod of length $0.5$ m slides at $2$ m/s on two parallel rails joined by a $1\ \Omega$ resistor, in a field of $1$ T perpendicular to the plane. The force needed to keep the rod moving at constant speed is (neglect other resistances)
Answer: (B) $0.5$ N
$\varepsilon = Blv = 1$ V, $I = 1$ A. Magnetic force on the rod $= BIl = 0.5$ N, opposing motion; the applied force must equal it.
Solution by Sreeraj P, M.Sc Physics