Editing Permeability (electromagnetism) (section)

{{Short description|Ability of magnetization}}
{{About|the magnetic constant|the analogous electric constant|permittivity}}
{{electromagnetism|cTopic=Magnetostatics}}

In [[electromagnetism]], '''permeability''' is the measure of [[magnetization]] produced in a material in response to an applied [[magnetic field]].  Permeability is typically represented by the (italicized) Greek letter [[Mu (letter)|''μ'']].  It is the ratio of the [[Magnetic field|magnetic induction]] <math>B</math> to the magnetizing field <math>H</math> in a material.  The term was coined by  [[William Thomson, 1st Baron Kelvin]] in 1872,<ref>[https://books.google.com/books?id=aApVAAAAMAAJ&pg=PA484 Magnetic Permeability, and Analogues in Electro-static Induction, Conduction of Heat, and Fluid Motion], March 1872.</ref> and used alongside [[permittivity]]  by [[Oliver Heaviside]] in 1885. The reciprocal of permeability is [[magnetic reluctivity]].

In [[SI]] units, permeability is measured in [[Henry (unit)|henries]] per [[Metre|meter]] (H/m), or equivalently in [[newton (unit)|newtons]] per [[ampere]] squared (N/A<sup>2</sup>). The permeability constant ''μ''<sub>0</sub>, also known as the [[magnetic constant]] or the permeability of free space, is the proportionality between magnetic induction and magnetizing force when forming a magnetic field in a classical [[vacuum]].

A closely related property of materials is [[magnetic susceptibility]], which is a [[Dimensionless quantity|dimensionless]] proportionality factor that indicates the degree of magnetization of a material in response to an applied magnetic field.