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The vacuum magnetic permeability (variously vacuum permeability, permeability of free space, permeability of vacuum, magnetic constant) is the magnetic permeability in a classical vacuum. It is a physical constant , conventionally written as μ 0 (pronounced "mu nought" or "mu zero").
As before, it is defined by the equation ε 0 = 1/(μ 0 c 2), and is thus determined by the value of μ 0, the magnetic vacuum permeability which in turn is determined by the experimentally determined dimensionless fine-structure constant α: = = ,
In SI units, permeability is measured in henries per meter (H/m), or equivalently in newtons per ampere squared (N/A 2). The permeability constant μ 0, 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.
is the speed of light (i.e. phase velocity) in a medium with permeability μ, and permittivity ε, and ∇ 2 is the Laplace operator. In a vacuum, v ph = c 0 = 299 792 458 m/s, a fundamental physical constant. [1] The electromagnetic wave equation derives from Maxwell's equations.
Its presently accepted value is [1] Z 0 = 376.730 313 412 (59) Ω, where Ω is the ohm, the SI unit of electrical resistance. The impedance of free space (that is, the wave impedance of a plane wave in free space) is equal to the product of the vacuum permeability μ 0 and the speed of light in vacuum c 0.
where μ 0 is the vacuum permeability (see table of physical constants), and (1 + χ v) is the relative permeability of the material. Thus the volume magnetic susceptibility χ v and the magnetic permeability μ are related by the following formula: = (+).
where is the vacuum permeability. Any magnetic field has an associated magnetic pressure contained by the boundary conditions on the field. It is identical to any other physical pressure except that it is carried by the magnetic field rather than (in the case of a gas ) by the kinetic energy of gas molecules.
The total energy in the space occupied by the system includes a component arising from the energy of a magnetic field in a vacuum. This component equals U v a c u u m = B e 2 V 2 μ 0 {\displaystyle U_{vacuum}={\frac {B_{e}^{2}V}{2\mu _{0}}}} , where μ 0 {\displaystyle \mu _{0}} is the permeability of free space , and isn't included as a part ...