Question

How would you demonstrate that momentary current can be obtained by suitable use of a magnet, a coil of wire, and a galvanometer?

Answer 1

A magnet is carried close to the current to create a magnetic field around the coil and then the coil generates electricity. If the coil is connected to a galvanometer, this will be deflected due to the flowing current.
The direction of the current of the coil depends upon the direction of the needle of the galvanometer. And The amount of deflection affects the amount of the current.
If the coil is moved towards the magnet then the electricity will also be generated.

Complete step by step answer:
In the first diagram and second diagram, Let $C$ be the circular coil, $M$ is the stable bar magnet along the axis of the coil, and $G$ is the galvanometer connected to the coil.

The direction of the current of the coil depends upon the direction of the needle of the galvanometer. And The amount of deflection affects the amount of the current.

First diagram shows that the nearer magnet pole of the coil is the north pole ($N$) and the direction of the motion of the magnet is towards the center of the coil. This implies that the direction of the induced current of the coil is anticlockwise.

The nearer magnet pole of the coil is the north pole ($N$) and if the direction of the motion of the magnet is away from the center of the coil then the direction of the induced current of the coil is clockwise.

For the second diagram, the nearer magnet pole of the coil is the south pole ($S$) and the direction of the motion of the magnet is towards the center of the coil. This implies that the direction of the induced current of the coil is clockwise.

The nearer magnet pole of the coil is the south pole ($S$) and if the direction of the motion of the magnet is away from the center of the coil then the direction of the induced current of the coil is anticlockwise.

Note: If the magnet is still positioned or moves around its axis, no current will be induced in the coil.

If the motion of the magnet is increased or decreased, the amount of the induced current is increased or decreased respectively.

If the coil is moved towards the magnet then the electricity will also be generated. Hence the relative motion of the coil and the magnet matters the most.