Magnets and their Properties

The phenomenon of magnetism was known to Greeks as early as 600 BC. They observed that some stones called magnetite (Fe₃O₄) attracted iron pieces. The pieces of naturally occurring magnetite are called natural magnets. Natural magnets are weak, but materials like iron, nickel, cobalt may be converted into strong permanent magnets. All magnets, natural or artificial, have same properties.

Properties of Magnets

(i) Directive Property: A small bar magnet, when suspended freely on its center of mass so as to rotate about a vertical axis, always stays in approximately geographical north-south direction.

(ii) Attractive Property: A magnet attracts small pieces of magnetic materials like iron, nickel and cobalt. The force of attraction is maximum at points near the ends of the magnet. These points are called poles of the magnet. In a freely suspended magnet, the pole which points towards the geographical north is called is north pole and the one which points towards the geographical south is called south pole.

(iii) Unlike poles of two magnets attract each other and like poles repel.

(iv) The poles of a magnet are inseparable. The simplest specimen providing magnetic field is a magnetic dipole.

(v) When a magnet is brought close to a piece of iron, the nearer end of the piece of iron acquires opposite polarity and the farther end acquires same polarity. This phenomenon is called magnetic induction.