Chapter-6|Electromagnetic Induction (EMI)| NCERT 12th Physics:
Energy Consideration: A Quantitative Study
Let r be the resistance of a movable arm PQ of the irregular conductor. We assume that the remaining arms QR, RS and SP have negligible resistances compare to r.
Due to the presence of the magnetic field, there is a force on arm PQ. This force is directed outwards in the direction opposite to the velocity of the rod.