MAGNETISM AND MATTER

INTRODUCTION


In 800 B.C. shepherds on the island of Magnetia in Greece observed that the nails in their shoes were glued to the ground due to presence of magnetic ores in the area. The word magnet owes its origin to this island of Magnetia.

Since 400 B.C., Chinese had been using magnetic needles to determine direction while sailing. Caravans used magnetic needles to navigate across the Gobi desert.

In 1600 A.D. William Gilbert, a physician with Queen Elizabeth-I, wrote a book “De Magnet” Some facts of magnetism given in the book are:

( 1 ) Earth behaves as a giant magnet with its magnetic field along north-south direction.

( 2 ) A bar magnet hung to freely rotate horizontally aligns itself along the north-south direction. The end pointing towards north is called its magnetic North Pole and the end pointing towards the south is called its magnetic South Pole.

( 3 ) Like magnetic poles repel each other, while unlike poles attract.

( 4 ) When a magnet is cut into pieces, each piece behaves as a magnet having both types of magnetic poles  (dipoles ). However, in an electric dipole, positive and negative charges can be separated and each is called an electric monopole. Magnetic monopole does not exist.

( 5 ) Magnets can be prepared using iron and its alloys.