Dielectric Constant

dielectric constant

[‚dī·ə′lek·trik ′kän·stənt]

(electricity)

For an isotropic medium, the ratio of the capacitance of a capacitor filled with a given dielectric to that of the same capacitor having only a vacuum as dielectric.

More generally, 1 + γχ, where γ is 4π in Gaussian and cgs electrostatic units or 1 in rationalized mks units, and χ is the electric susceptibility tensor. Also known as relative dielectric constant; relative permittivity; specific inductive capacity (SIC).

Dielectric Constant

 

a quantity that characterizes the dielectric properties of a medium—its reaction to an electrical field. In the relation D = ∊E, where E is the field strength and D is the electrical induction in the medium, the dielectric constant is the proportionality factor ∊. For most dielectrics, the dielectric constant in fields that are not very strong is not a function of the field E. In strong fields (comparable to intra-atomic fields), and for certain dielectrics (such as ferroelectric materials) in ordinary fields, the relationship between D and E is nonlinear.

The value of the dielectric constant depends essentially on the type of substance and on the external conditions (temperature, pressure, and so on). In alternating electrical fields the dielectric constant is a function of the frequency of the field E.