electric susceptibility

Elect.

(when the components of electrical polarization are linear combinations of the components of the electric field) the coefficient or set of coefficients that multiply the components of the electric field. Also called susceptibility. Cf. polarization (def. 3b).

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▪ physics

      quantitative measure of the extent to which an electric field applied to a dielectric material causes polarization, the slight displacement of positive and negative charge within the material. For most linear dielectric materials, the polarization P is directly proportional to the average electric field strength E so that the ratio of the two, P/E, is a constant that expresses an intrinsic property of the material. The electric susceptibility, χ_e, in the centimetre-gram-second (cgs) system, is defined by this ratio; that is, χ_e = P/E. In the metre-kilogram-second (mks) system, electric susceptibility is defined slightly differently by including the constant permittivity of a vacuum, ε₀, in the expression; that is, χ_e = P/(ε₀E). In both systems the electric susceptibility is always a dimensionless positive number. Because of the slight difference in definition, the value of the electric susceptibility of a given material in the mks system is 4π times its value in the cgs system.

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