Question

A magnet is passed back and forth through a coil connected to a light bulb. The light bulb lights up. Why?

Answer 1

Answer:

From Faraday's law of Induction: A changing magnetic field induces emf in the coil.

Explanation:

Faraday's law states that when a coil is run through a changing magnetic field or a magnet is passed back and forth through a coil, an emf is induced which produces electric current in the coil.

Changing magnetic flux induces electromotive force.

$e = - \frac{d\phi}{dt} = -\frac{dB A}{dt}$

When the magnet is passed back and forth, it causes a changing magnetic flux around the coil. This induces emf and the current flows which lights up the bulb connected to it.

Answer 2

The moving back and forth of the magnetic causes a changing magnetic field, which  induces an Emf through the coils of the wire and so the bulb ligts up.