Fun With Magnets

Fun With Magnets

 INTRODUCTION:
Magnetic phenomena are universal in nature. Vast, distant galaxies, the tiny invisible atoms, men and beasts all are permeated throug h and through with a host of magnetic fields from a variety of sources. The earth magnetism predates human evolution. The word magnet is derived from the name of an island in Greece called magnesia where magnetic ore deposits were found, as early as 600 BC. Shepherds on this island complained that their wooden shoes (which had nails) at times stayed struck to the ground. Their iron-tipped rods were similarly affected. This attractive property of magnets made it difficult for them to move around. The directional property of magnets was also known since ancient times. A thin long piece of a magnet, when suspended freely, pointed in the north-south direction. A similar effect was observed when it was placed on a piece of cork which was then allowed to float in still water. The name lodestone (or loadstone) given to a naturally occurring ore of iron- magnetite means leading stone. The technological exploitation of this property is generally credited to the Chinese. Chinese texts dating 400 BC mention the use of magnetic needles for navigation on ships. Caravans crossing the Gobi desert also employed magnetic needles.
A Chinese legend narrates the tale of the victory of the emperor Huang-ti about four thousand years ago, which he owed to his craftsmen (whom now a days you would call engineers).

HOW MAGNETS WERE DISCOVERED
It is said that, there was a shepherd named Magnes, who lived in ancient Greece. He used to take his herd of sheep and goats to the nearby mountains for grazing. He would take a stick with him to control his herd. The stick had a small piece of iron attached at one end. One day he was surprised to find that he had to pull hard to free his stick from a rock on themountainside (Fig. ). It seemed as if the stick was being attracted by the rock. The rock was a natural magnet  and it attracted the iron tip of the shepherd's stick. It is said that this is how natural magnets were discovered. Such rocks were given the name magnetite, perhaps after the name of that shepherd. Magnetite contains iron. Some people believe that magnetite wasfirst discovered at place called Magnesia. The substances having the property of attracting iron are now known as magnets. This is how the story goes.

In any case, people now have discovered that certain rocks have the property of attracting pieces of iron. They also found that small pieces of these rocks have some special properties. They named these naturally occurring materials magnets. Later on the process of making magnets from pieces of iron was discovered. These are known as  artificial magnets. 
Now adays artificial magnets are prepared in different shapes. For example, bar magnet, horse- shoe magnet, cylindrical or a ball-ended magnet.  below Fig. shows a few such magnets.
 

MAGNETIC AND NON - MAGNETIC MATERIALS
Magnetic substances are substances that get attracted to magnets. Few of the magnetic substances are - iron, steel, cobalt and nickel. Non-magnetic substances are substances that do not get attracted by a magnet. Few of the materials are wood, plastic, copper, rubber.
Non-magnetic materials do not get attracted to a magnet. Examples of non-magnetic material are wood, plastic, etc. ... Non-magnetic substances are made of molecules where the electrons spinning in one direction are balanced by the electrons spinning in the opposite direction.
The easiest way to tell them apart is that a magnet can repel and attract another magnet. Whereas, a piece of magnetic material can only attract a magnet! Magnetic materials do not have fields around them, but they are affected by near by magnetic fields.