Permeability
According to electromagnetism, permeability is the ability of
a material to support the creation of magnetic field by itself. It is a degree
of magnetization that a material contains the response to the magnetic field.
SI Unit
In SI unit, permeability is measured in henries per meter (H·m−1 ) and in
newton per ampere squared (N·A−2). Permeability has a constant which is called
permeability constant and it is denoted by µ0.
It is also known as magnetic constant.
Explanation
In electromagnetism,
the auxiliary magnetic field H represents the magnetic field B that influences
the magnetic dipoles to the required medium. Which includes dipole migration
and magnetic dipole. Its relation is as follows:
Here µ is the permeability B is the magnetic field
which is measured in webers per square meters (V·s/m2) or tesla (T) and H is the auxiliary magnetic field measured in amperes
per meter(A·m−1).
Relative Permeability and Susceptibility
Relative
permeability is the ratio between the permeability of specific medium and
permeability of free space which is denoted by µ0 and relative permeability is denoted by µr.
Its formula is given below:
The magnetic susceptibility is
given as:
Here Xm is a quantity which has no
dimension to distinguish it from Xp (specific susceptibility) and Xm (molar mass susceptibility).
Complex permeability
Complex permeability is a tool which
is used to deal with high frequency magnetic effects. At low frequencies in a
linear material, the magnetic field and the auxiliary magnetic field are
proportional to each other by some scalar permeability. At high frequencies,
these quantities will start reacting to each other with lagging characteristics
according to time. These fields are called phasors, such as:
Here
is the phase delay of B from
H. The ratio of the phasors can be written as:
is the phase delay of B from
H. The ratio of the phasors can be written as:
so that the permeability
becomes a complex number. By Euler's formula, the complex
permeability can be translated from polar to rectangular form which is
given below:
The ratio of the imaginary
to the real part of the complex permeability is called the loss
tangent,
This value helps us to provide a
measure of how much power is lost from the material and how much power is
stored in the material.
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