Magnets have been one of the most useful materials discovered and have been the source for much wonder and entertainment. Since their discovery thousands of years ago, people have found uses for magnets in all types of equipment. From compasses to cabinet doors, most people encounter magnets on a daily basis, yet many do not fully understand how they work.
Ferrous metal is defined as any metal that contains iron. Ferrous metals are very common due to the heavy use of iron in most metal alloys. Ferrous metals contain a large enough iron content to create enough domains for a magnetic field to act on and attract. Ferrous materials are the only objects that are physically attracted to magnetic fields.
Domains are the primary reason that magnets work only with ferrous material. Domains are the small individual magnetic fields that surround a cluster of iron molecules. Each domain has its own individual polar alignment and each domain's polar line can face in different directions from the rest of the surrounding molecules. The scrambled order of these domains is the reason that iron, in and of itself, is not magnetic but can be acted on by other magnets. Domains are found naturally in ferrous metals and can be created temporarily by a flowing electric current.
How they work
Magnetic fields are created when the multitude of individual domains line up through external forces. Domains can line up by exposure to an electrical current or even physical movement against another magnetized object. Ferrous objects are attracted to magnetic fields when the individual domains line up with the electrical fields. It is possible to magnetize most ferrous objects simply by rubbing them against a magnet repeatedly. Once the domains of the iron molecule are aligned and facing in the same polar direction, their unison creates a magnetic field of its own that can act on other ferrous material.
Natural magnets are what led to the original discovery of magnets. Magnetite is one of the most common metals that is considered a natural magnet. Magnetite is a metal whose atomic construction is easily magnetized by simply being in contact with other metallic objects. The Vikings and the Chinese used magnetite in the first compasses.
Electromagnets are created by running an electrical current through a conductive metal. An electrical current causes the rapid movement of electrons, which creates a magnetic field. Electromagnetic fields can be created by running an electrical current through any metal, including non-ferrous conductive metals.