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Chapter V Dielectric Study of ……
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macroscopic charge transport and in the case when the migrating charge
carriers are ions, a macroscopic mass transport as well.
The electric response of a normal dielectric can be explained by its
dielectric strength (breakdown strength), conductivity, dielectric loss, and
dielectric constant. The behavior of nonlinear dielectric depends on the
amplitude and time variation of the electric field.
Dielectric strength is defined as the maximum electric field, which can
be applied to a dielectric without causing breakdown, the abrupt irreversible
drop in resistively at high fields often accompanied by destruction of the
material. Dielectric strength of most insulating materials is in the range from
10 4 to 10 7 V/m. at room temperature and low frequencies and it decreases at
higher temperatures.
5.4 Permittivity in the Medium
In the general case of isotropic media, D and E are parallel vectors and
is a scalar, but in anisotropic media it is rank-2 tensor (causing
birefringence). The permittivity and magnetic permeability of a medium
together determine the phase velocity v of the electromagnetic radiation
through that medium, =
When an electric field is applied to a medium, a current flows and the
current flowing in real medium is made up of two parts; such as conduction
and displacement current. The displacement current can be considered as the
elastic response of the material to the applied electric field. As the magnitude
of the electric field increases, the displacement current is stored in the
material when the electric field decreases the material releases the
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