Magnetism and Electrodynamics

Abstract

Everybody knows that a magnet is a piece of iron the two ends (or poles) of which exert or suffer forces of a particular kind. The simplest form is the straight bar magnet, and the type most commonly used is the U-shaped horseshoe magnet. The following phenomena are readily observed with a magnet:

• (1) both poles of a magnet attract “unmagneitzed” pieces of iron;

• (2) the pole a magnet attracts one pole of another magnet but repels its other pole;

• (3) a magnet capable of free rotation in all directions adopts such a position that the line connecting its two poles — in a bar magnet therefore its axis — points in a direction not far removed from that of the geographic north and south.