Magnetism

Magnetism is the class of physical attributes that occur through a magnetic field. This lets objects pull together or push apart. It is one of two parts of electromagnetism, the other part being electricity. Both electric currents and tiny particles called elementary particles can make magnetic fields.

The most common effects of magnetism happen with materials called ferromagnetic materials. These include iron, cobalt, and nickel. They are strongly pulled toward magnets and can even become permanent magnets. This means they can make their own magnetic fields after being near one.

Not all materials act the same with magnets. Some, like aluminium and oxygen, are very weakly pulled toward a magnetic field. Others, like copper and carbon, are very slightly pushed away. These effects are usually too small to see without special tools.

The strength of a magnetic field gets weaker when you move farther away from the source of the magnetism. Many things can change how strong a magnetic field is, such as the type of material, its shape, electric currents nearby, and even the temperature of the object.

History

Main article: History of electromagnetic theory

Magnetism was first noticed long ago when people found special stones, called lodestones, that could pull iron toward them. These stones are made from a mineral called magnetite.

Long ago in Greece, a thinker named Thales talked about magnetism. In India, an old medical book told how to use magnetite to help remove arrows from someone's body.

In China, very old books wrote about how lodestones could make iron come close. A Chinese scientist named Shen Kuo wrote about using a special compass with a lodestone spoon to help people find their way.

Later, people in Europe also began to write about compasses and magnets. An important book about magnets was written by Peter Peregrinus de Maricourt in 1269.

In 1600, a scientist named William Gilbert did many tests and learned that Earth itself acts like a big magnet. This helped explain why compasses point north.

Later, scientists found that electricity and magnetism are connected. In 1819, Hans Christian Ørsted discovered that electric currents can create magnetic fields. These ideas helped create the science of electromagnetism.