Permeability (electromagnetism)
In electromagnetism, permeability is the degree of magnetisation of a material in response to a magnetic field. Absolute permeability is represented by the symbol μ.
- <math>\mu = \frac {B} {H},<math>
where B is the magnetic flux density (also called the magnetic induction) in the material and H is the magnetic field strength.
In SI units, magnetic flux density is measured in tesla, magnetic field strength in ampere per metre and permeability in henrys per metre.
Absolute permeability
Absolute permeability is represented by the symbol μ0 and is the permeability of the vacuum, where μ0 = 4π × 10−7 N A−2 (exactly).
Together with permittivity, permeability defines the speed of light.
Relative permeability
Relative permeability, sometimes denoted by the symbol μr, is the ratio of the permeability of a specific medium to the permeability of free space μ0:
- <math>\mu_{r} = \frac{\mu}{\mu_{0}} <math>
| Relative permeability for some materials
|
| Medium
| <math>\chi_m = \mu_r - 1<math>
|
| Hydrogen
| <math>0{,}008\cdot10^{-6}<math>
|
| Copper
| <math>-6{,}4\cdot10^{-6}<math>
|
| Water
| <math>-8{,}0\cdot10^{-6}<math>
|
| Aluminium
| <math>22{,}2\cdot10^{-6}<math>
|
| Platin
| <math>265\cdot10^{-6}<math>
|
