Magnet

A magnet is a material or object that produces a <a href="/facts/Magnetic_field/Ta8Ev588">magnetic field</a>. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other <a href="/facts/Ferromagnetic_material/fH3HFnSl">ferromagnetic materials</a>, such as <a href="/facts/Iron/QK1JYy8E">iron</a>, <a href="/facts/Steel/aN6qWo4H">steel</a>, <a href="/facts/Nickel/KwMCHYRP">nickel</a>, <a href="/facts/Cobalt/gqhScEw4">cobalt</a>, etc. and attracts or repels other magnets.
A permanent magnet is an object made from a material that is <a href="/facts/Magnetize/eo75vApl">magnetized</a> and creates its own persistent magnetic field. An everyday example is a <a href="/facts/Refrigerator_magnet/4WL3E5UY">refrigerator magnet</a> used to hold notes on a refrigerator door. Materials that can be magnetized, which are also the ones that are strongly attracted to a magnet, are called <a href="/facts/Ferromagnetism/fH3HFnSl">ferromagnetic</a> (or <a href="/facts/Ferrimagnetic/sMcg7RYt">ferrimagnetic</a>). These include the elements <a href="/facts/Iron/QK1JYy8E">iron</a>, <a href="/facts/Nickel/KwMCHYRP">nickel</a> and <a href="/facts/Cobalt/gqhScEw4">cobalt</a> and their alloys, some alloys of <a href="/facts/Rare-earth_element/PQSUQumk">rare-earth metals</a>, and some naturally occurring minerals such as <a href="/facts/Lodestone/8bqkYHbR">lodestone</a>. Although ferromagnetic (and ferrimagnetic) materials are the only ones attracted to a magnet strongly enough to be commonly considered magnetic, all other substances respond weakly to a magnetic field, by one of several other types of <a href="/facts/Magnetism/eo75vApl">magnetism</a>.
Ferromagnetic materials can be divided into magnetically "soft" materials like <a href="/facts/Annealing_(metallurgy)/2AfoCE4X">annealed</a> <a href="/facts/Iron/QK1JYy8E">iron</a>, which can be magnetized but do not tend to stay magnetized, and magnetically "hard" materials, which do. Permanent magnets are made from "hard" ferromagnetic materials such as <a href="/facts/Alnico/gEW0Itz3">alnico</a> and <a href="/facts/Ferrite_(magnet)/kBTM7Dqk">ferrite</a> that are subjected to special processing in a strong magnetic field during manufacture to align their internal <a href="/facts/Crystallite/nXSgR0wp">microcrystalline</a> structure, making them very hard to demagnetize. To demagnetize a saturated magnet, a certain magnetic field must be applied, and this threshold depends on <a href="/facts/Coercivity/duBA23fB">coercivity</a> of the respective material. "Hard" materials have high coercivity, whereas "soft" materials have low coercivity. The overall strength of a magnet is measured by its <a href="/facts/Magnetic_moment/VpAQKJtr">magnetic moment</a> or, alternatively, the total <a href="/facts/Magnetic_flux/jQMVxrnD">magnetic flux</a> it produces. The local strength of magnetism in a material is measured by its <a href="/facts/Magnetization/zxrtXzTN">magnetization</a>.
An <a href="/facts/Electromagnet/3YMYtSMX">electromagnet</a> is made from a coil of wire that acts as a magnet when an <a href="/facts/Electric_current/Dc1xdnUX">electric current</a> passes through it but stops being a magnet when the current stops. Often, the coil is wrapped around a <a href="/facts/Magnetic_core/yojywmuo">core</a> of "soft" ferromagnetic material such as <a href="/facts/Mild_steel/QGYURvFA">mild steel</a>, which greatly enhances the magnetic field produced by the coil.

Magnet open-in-new

Magnet