Magnets have been used by people for a very long time. Hindu scriptures refer to medical applications of magnets as far back as the 40th century B.C.; the ancient Chinese, Greeks, Egyptians and Romans also used magnets with medicine. Magnets have helped ancient and modern explorers navigate, through the use of the compass. With the industrial revolution and then the advent of electricity, magnets came to be used in a wide variety of devices.
A magnet is anything that produces its own magnetic field. This magnetic field allows a magnet to exert force on certain metals, called ferromagnetic material. Some metals, such as copper, gold, aluminum and silver, are not ferromagnetic. There are two kinds of magnets: permanent and electromagnets. Unlike most materials, in which electrons spin in random directions, permanent magnets have electrons that all spin in the same direction. This results in a magnetic field. Electromagnets use electricity passing through a coil of wires to create their magnetic fields.
Magnets for Information Storage
Computers, cassette tapes and credit cards use a series of very small magnetic fields to store information. Computers process information in binary, the base-2 units of which correspond to a magnetic field aligned to either the north or the south. These fields are spun, in the case of a hard disk, or wound, in the case of a cassette, allowing a magnetic sensor to read them.
Common Appliances That Use Magnets
Electric motors use electricity and magnetic fields to create force, so nearly any appliance that uses electricity to create motion involves magnets. Some examples are blenders, garage door openers and dishwashers. Old television sets and monitors use magnetic fields to manipulate a stream of electrons to form images. Speakers, headphones, telephones and doorbells use magnets to create sound. Magnets are included in items such as shoes and mattress pads to provide relief from pain.
Industrial Uses for Magnets
Magnets are used industrially for a variety of purposes. Magnetic sweepers allow people to easily clean up fragments of waste metal. Miners use magnets to help pull the metal out of the ore. Food manufacturers use magnets to keep small iron particles out of food. Vending machines use magnets to differentiate coins from other material. Large electromagnets are used in construction and at junkyards to move materials.
Other Devices That Use Magnets
People continue to find new and interesting applications for magnets. Magnetic Resonance Imaging (MRI) scans use magnets to align hydrogen atoms in the body, which helps to produce detailed three dimensional images of areas in a patient's body. Magnets are used by researchers to bring particles up to relativistic speeds. Magnets are used in a similar way on a large scale to suspend and accelerate maglev trains, which are capable of achieving incredible speeds.