Topic: Dielectric

Dielectric

A dielectric is the electrically insulating material between the metallic plates of a capacitor. A good dielectric typically contains polar molecules that reorient in external electric field. This dielectric polarization increases the capacitor's capacitance.

Generalizing this, any insulating substance can be called a dielectric. While the term "insulator" refers to a low degree of electrical conduction, the term "dielectric" is typically used to describe materials with a high polarization density.

Generalizing further, dielectrics, the study of dielectric properties, is concerned with the storage and dissipation of electric and magnetic energy in materials. It is important to explain various phenomena in electronics, optics, and solid-state physics.



The electric susceptibility χe of a dielectric material is a measure of how easily it polarizes in response to an electric field. This, in turn, determines the electric permittivity of the material and thus influences many other phenomena in that medium, from the capacitance of capacitors to the speed of light.

It is defined as the constant of proportionality (which may be a tensor) relating an electric field E to the induced dielectric polarization density P such that

where \, \varepsilon_0 is the electric permittivity of free space.

The susceptibility of a medium is related to its relative permittivity by

So in the case of a vacuum,