JEE ADVANCED PHYSICS QUESTION SEPTEMBER 2020
Answers
A light disc made of aluminium is kept horizontally and is free to rotate about its axis as shown in figure. A strong magnet is held vertically at a point above the disc away from its axis. on revolving the magnet about the axis of the disc, the disc will (figure is schematic and not drawn to scale ) ...
solution : The disc will rotate in the same direction as the direction of magnet's motion.
reason : when the magnet is moved, it creates a state where the plate moves through the magnetic flux. due to electromotive force is generated in the plate, induced currents are produced. [ as we know, from Faraday's law, negative of change in flux with respect to time gives induced emf. ] so these current opposes the relative motion so disc will rotate in the direction of rotation of magnet.
Therefore the correct option is (B)