Magnetic field

A magnetic field (sometimes called B-field) is a <a href="/facts/Physical_field/FJdAKeRA">physical field</a> that describes the magnetic influence on moving <a href="/facts/Electric_charge/xxsBfmlB">electric charges</a>, <a href="/facts/Electric_currents/Dc1xdnUX">electric currents</a>,: ch1  and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to the magnetic field.: ch13 : 278  A <a href="/facts/Permanent_magnet/vvrg6VSk">permanent magnet</a>'s magnetic field pulls on <a href="/facts/Ferromagnetic_material/fH3HFnSl">ferromagnetic materials</a> such as <a href="/facts/Iron/QK1JYy8E">iron</a>, and attracts or repels other magnets. In addition, a nonuniform magnetic field exerts minuscule forces on "nonmagnetic" materials by three other magnetic effects: <a href="/facts/Paramagnetism/vj1SMbbp">paramagnetism</a>, <a href="/facts/Diamagnetism/dgFavn9K">diamagnetism</a>, and <a href="/facts/Antiferromagnetism/aQ124Kh7">antiferromagnetism</a>, although these forces are usually so small they can only be detected by laboratory equipment. Magnetic fields surround magnetized materials, electric currents, and <a href="/facts/Electric_field/tt4MooBs">electric fields</a> varying in time. Since both strength and direction of a magnetic field may vary with location, it is described mathematically by a <a href="/facts/Function_(mathematics)/CdReEKCh">function</a> assigning a <a href="/facts/Euclidean_vector/bCLrdksy">vector</a> to each point of space, called a <a href="/facts/Vector_field/ccFNuPPp">vector field</a> (more precisely, a <a href="/facts/Pseudovector/c3b5GgWD">pseudovector</a> field).
In <a href="/facts/Electromagnetics/oAkmALHT">electromagnetics</a>, the term magnetic field is used for two distinct but closely related vector fields denoted by the symbols B and H. In the <a href="/facts/International_System_of_Units/S7YLglNz">International System of Units</a>, the unit of B, <a href="/facts/Magnetic_flux/jQMVxrnD">magnetic flux</a> density, is the <a href="/facts/Tesla_(unit)/K6I5Stn9">tesla</a> (in SI base units: kilogram per second squared per ampere),: 21  which is equivalent to <a href="/facts/Newton_(unit)/Ral9XgNl">newton</a> per meter per ampere. The unit of H, magnetic field strength, is <a href="/facts/Ampere/MScqkCgz">ampere</a> per meter (A/m).: 22  B and H differ in how they take the medium and/or magnetization into account. In <a href="/facts/Vacuum/BTk3goyV">vacuum</a>, the two fields are related through the <a href="/facts/Vacuum_permeability/nKxRk6J1">vacuum permeability</a>, 
 
 
 
 
 B
 
 
 /
 
 
 μ
 
 0
 
 
 =
 
 H
 
 
 
 {\displaystyle \mathbf {B} /\mu _{0}=\mathbf {H} }
 
; in a magnetized material, the quantities on each side of this equation differ by the <a href="/facts/Magnetization/zxrtXzTN">magnetization</a> field of the material.
Magnetic fields are produced by moving electric charges and the intrinsic <a href="/facts/Magnetic_moment/VpAQKJtr">magnetic moments</a> of <a href="/facts/Elementary_particle/CTFDM97U">elementary particles</a> associated with a fundamental quantum property, their <a href="/facts/Spin_(physics)/4Jvp7e8P">spin</a>.: ch1  Magnetic fields and <a href="/facts/Electric_field/tt4MooBs">electric fields</a> are interrelated and are both components of the <a href="/facts/Electromagnetic_force/oAkmALHT">electromagnetic force</a>, one of the four <a href="/facts/Fundamental_force/WrFEJaFl">fundamental forces</a> of nature.
Magnetic fields are used throughout modern technology, particularly in <a href="/facts/Electrical_engineering/YYXW1KLW">electrical engineering</a> and <a href="/facts/Electromechanics/0D5gkXko">electromechanics</a>. Rotating magnetic fields are used in both <a href="/facts/Electric_motor/ArD7BGDa">electric motors</a> and <a href="/facts/Electric_generator/5sATsUGX">generators</a>. The interaction of magnetic fields in electric devices such as transformers is conceptualized and investigated as <a href="/facts/Magnetic_circuit/KUURNlXM">magnetic circuits</a>. Magnetic forces give information about the charge carriers in a material through the <a href="/facts/Hall_effect/4r86ffPr">Hall effect</a>. The Earth produces <a href="/facts/Earth%27s_magnetic_field/73G36wmx">its own magnetic field</a>, which shields the Earth's ozone layer from the <a href="/facts/Solar_wind/BvuB3dT8">solar wind</a> and is important in <a href="/facts/Navigation/sGGAJ0AQ">navigation</a> using a <a href="/facts/Compass/86MaeFXu">compass</a>.

Magnetic field open-in-new

Magnetic field