MAGNETISATION BY ELECTRIC CURRENT

There are mainly two methods by which Artificial Magnets are made:

1. By Rubbing

A steel piece may be magnetized by repeatedly rubbing a magnet over its entire length in same direction. In this way the steel piece is covered into a magnet its first terminal having the same (and the last terminal having the opposite) polarity to that of the magnet used for rubbing.

2. By Electric Current

Another (and a more convenient, suitable and effective) method of magnetization is by passing a current in a coil of insulated copper wound round a piece of soft iron.

The soft iron rod will have magnetization lasting so long as the current flows. But if the piece inside the coil is of steel, it is found to have acquired a permanent magnetization.

The polarity developed at any end of the rod is determined by the direction of flow of current in the coil. If on looking at one end of the magnet current appears to flow anticlockwise, then that end of the rod behaves as a north-pole, and if it appears to flow clockwise, the end would be the south pole.

Direction of Flow of Electric Current

This rule can be easily remembered by considering the letters N and S to move.