Physics MAGNETIC INTENSITY AND PERMEABILITY

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MAGNETIC INTENSITY AND PERMEABILITY

Magnetic Intensity

The magnetic field in "empty" space is denoted by the symbol `B`. It is calculated from Ampere's Law or Biot-Savart's Law and measured in tesla. However, when the magnetic field passes through a magnetically responsive material, such as iron, the material itself contributes its internal magnetic field. Then a second quantity, H called as magnetic field intensity is used to characterize the strength of external field i.e. the magnetic field due to the external sources (electric current) only, excluding the contribution due to material's internal magnetic field.

`H=B/mu_0 - M`

where H has the same dimensions as M and is measured in units of `A m^(-1)`.
Thus, the total magnetic field B is written as

`B= mu_0(H+M)`

Permeability

The magnetic permeability of a substance is a measure of its conduction of magnetic lines of force through it. It is defined as the ratio of the magnetic induction B inside the magnetized substance to the magnetic intensity H of the magnetizing field, that is,

`mu=B/H`

SI unit of permeability is `NA^(-2)` or `TmA^(-1)` or `WbA^(-1)m^(-1)`

`text(Relative Magnetic Permeability :)` `(mu_r)`

`mu_r=mu/mu_0`

`mu_r=B/B_0`

B = Magnetic flux density

`B_0` = Magnetic flux density in vacuum