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It is a physical constant, conventionally written as μ 0 (pronounced "mu nought" or "mu zero"). It quantifies the strength of the magnetic field induced by an electric current. Expressed in terms of SI base units, it has the unit kg⋅m⋅s −2 ⋅A −2. It can be also expressed in terms of SI derived units, N⋅A −2.
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 .
The constants listed here are known values of physical constants expressed in SI units; that is, physical quantities that are generally believed to be universal in nature and thus are independent of the unit system in which they are measured. Many of these are redundant, in the sense that they obey a known relationship with other physical ...
The shed is a unit of area used in nuclear physics equal to 10 −24 barns (100 rm 2 = 10 −52 m 2). The outhouse is a unit of area used in nuclear physics equal to 10 −6 barns (100 am 2 = 10 −34 m 2). The barn (b) is a unit of area used in nuclear physics equal to one hundred femtometres squared (100 fm 2 = 10 −28 m 2).
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.
Gaussian units constitute a metric system of units of measurement. This system is the most common of the several electromagnetic unit systems based on the centimetre–gram–second system of units (CGS). It is also called the Gaussian unit system, Gaussian-cgs units, or often just cgs units.
The ampere was redefined by defining the elementary charge as an exact number of coulombs as from 20 May 2019, [4] with the effect that the vacuum electric permittivity no longer has an exactly determined value in SI units. The value of the electron charge became a numerically defined quantity, not measured, making μ 0 a measured
In SI units, the energy density of a magnetic field with strength can be expressed as = where is the vacuum permeability. Any magnetic field has an associated magnetic pressure contained by the boundary conditions on the field.