Question

A bar magnet M is dropped so that it falls vertically through the coil C. The graph obtained for voltage produced across the coil V/S time is shown:-

Explain the shape of the graph.

Why is negative peak longer than positive peak ?

Answer 1

Answer 1. The rate of flux increases initially and reaches a maximum, after which it decreases and becomes zero. So, the shape of the graph could be a downward parabola.

Answer 2. The negative peak tends to be longer than the positive peak because the magnet moves faster when it is going out of the coil than while moving into the coil. When the magnet enters the coil, the fall of the magnet is resisted by the back emf of the coil. But when the magnet exits the coil, there will not be any back emf to resist this fall. Therefore, the magnet will fall freely and quickly due to the gravity pull.