With reference to where a small bar magnet M approaches a coil C (with ends connected to a galvanometer), show that, Lenz's law is consistent with the principle of conservation of energy. What will be the magnetic polarity of the coil according to the diagram, as the magnet moves through it and comes out from the left?

Explanation

According to Lenz's law, the direction of induced current in the coil will be such that, the end Q opposes the motion of the magnet. Hence, a north pole is generated at the end Q, i.e., the direction of current is anticlockwise. To continue the motion of the magnet against the repulsive force between the magnet and the coil, some external work must be done. This external work is converted into electrical energy in the coil. Hence, Lenz's law is in accordance with the law of conservation of energy.
If the magnet moves through the coil and comes out from left, the induced current in the coil again opposes that motion, i.e., the end P attracts the S -pole. So, the direction of current in the coil will be reversed. This event can be noticed with the help of the galvanometer G.