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Electric susceptibility



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A dimensionless parameter measuring the ease of polarization of a dielectric. In a vacuum, the electric flux density D (measured in coulombs/m2 and electric field strength E (volts/m) are related by Eq. (1) where e is

D = ε0E (1)

the permittivity of free space, having the value 8.854 x 10-12 farad/m. In a dielectric material, polarization occurs, and the flux density has the value given by Eq. (2), where Er is the relative

D = ε0εr E = ε0E + P (2)

permittivity of the material and P is the polarization flux density. This can be written as Eq. (3), where Χe = εr - 1 is known as the

P = ε0r — 1)E = E0ΧeE

electric susceptibility of the dielectric material. It's a measure of that part of the relative permittivity which is due to the material itself.



The electric susceptibility can be related to the polarizability a by expressing the polarization in terms of molecular parameters. Thus Eqs. (4) hold, where N is the number of molecules per unit

P = N(μ)avg = NαEL

Χe =((NαEL)/e0E))

volume, (μavg) is their average dipole moment, and EL is the local electric field strength at a molecular site. At low concentrations, EL approaches E, and the susceptibility is proportional to the concentration N. For a discussion of the properties and measurement of electric susceptibility Google POLARIZATION OF DIELECTRICS.

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Updated: Friday, 2007-11-16 17:27 PST