Substation1
Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

dielectric
(1) a medium that exhibits negligible or no electrical conductivity and thus acts as a good electrical insulator.
(2) a medium characterized by zero conductivity, unity relative permeability, and a relative permittivity greater than one. Also known as an insulator.
dielectric constant
(1) a quantity that describes how a material stores and dissipates electrical energy.
(2) ratio of the electrical capacity of a condenser, which has a given material as the dielectric, to the capacity of an identical condenser, but with air as the dielectric.
(3) permittivity of a medium normalized to the permittivity of free space; a measure of the response of a dielectric to an applied electric field.
(4) an electric property of an insulator or semi-conducting material, which describes how differently electric fields will behave inside of the material as compared to air. As an example, er = 12.9 for GaAs as compared to er = 1 for air. In integrated circuits, an effective dielectric constant (eeff) is used, since the electric fields supported by the signals traveling through the conductors on the circuit flow through both air and the insulator or semiconductor simultaneously.