What is magnetism?

          Magnetism owes its name to the fact that the early Greeks found the natural magnetic material called Lodestone, in an area called Magnesia, a province of Asia Minor in 800 B.C. This stone was of black colour and an ore of iron called magnetite. This stone has several interesting properties.

          Firstly, it has a strong attraction for iron. On experimenting, it was found that if a piece of lodestone was dipped in iron fillings and then lifted out, the fillings mainly get attached to certain parts, the other parts remaining bare. These regions of greatest attraction were called the poles and the place where there was little attraction was called a neutral region.

          It was also discovered that if a piece of lodestone was suspended by a thread or floated on a piece of wood, it came to rest in a definite direction — pointing towards north and south. The part pointing towards the north was called the North Pole, and the one pointing towards the south was called the South Pole. This property was used by the Chinese in the 13th century to make use of magnets as compasses for finding the direction in sea voyages.

          Experiments in this field further revealed that if two lodestones were brought together, the north and south poles attracted each other while the north-north and south-south poles repelled each other. This established the fact that dissimilar poles attract each other and similar poles repelled each other.

          If a bar of iron or steel is rubbed from one end to the other end with a piece of lodestone, it also acquires magnetic properties and becomes a magnet. Such a magnet is known as an artificial magnet.

          Gradually scientists working in this field also discovered that a magnet could be made by winding an insulated wire around a piece of iron and passing an electric current through it. This is called an electromagnet. Such magnets are used in electric motors.

          The next important discovery in the field of magnetism came in 1600. The English scientist, Sir William Gilbert, suggested that the earth was a giant magnet. Thus he explained why a freely suspended magnet points to the north and south of the Earth. 

          During the next few hundred years, more discoveries were made in the field of magnetism. However the phenomenon of magnetism was not properly understood, until the 19th century.

          Now scientists know that magnetism is caused by moving electrons. All matter is made up of atoms, and atoms have a central core called nucleus, around which electrons revolve in different orbits. These electrons carry negative charge. Whenever an electric charge moves, it produces a magnetic effect. So the moving electrons make a substance magnetic. Sometimes the magnetism of different electrons makes a substance magnetic. Sometimes the magnetism of different electrons in each atom gets neutralized. That is why some materials are non-magnetic in nature. In fact the magnetic materials have magnetic domains which on magnetization get lined up and the substance becomes a strong magnet. When a magnet is cut or broken each piece is still magnetic because its domains are still lined up.

          Magnetism occurs most strongly in three metals: iron, cobalt and nickel. These metals can be used to make strong magnets. Iron is most commonly used because it is the cheapest and easily available of the three metals. Usually magnets are made of steel — an alloy of iron.

           Magnets are very useful in our daily life. They are used in making the Mariner’s compass to guide ships. They are also used in radio sets, television sets, telephones, microphones and in many other electronic instruments, such as electric generators and motors.