10.5: Electric Permittivity

A Describe the electric permittivity of a material or medium

10.5.A.1 Electric permittivity is a measurement of the degree to which a material or medium is polarized in the presence of an electric field.

10.5.A.2 Electric polarization can be modeled as the induced rearrangement of electrons by an external electric field, resulting in a separation of positive and negative charges within a material or medium.

10.5.A.3 Free space has a constant value of electric permittivity  _ 0that appears in physical relationships.

In electromagnetism, the absolute permittivity, often simply called permittivity and denoted by the Greek letter ε (epsilon), is a measure of the electric polarizability of a dielectric. A material with high permittivity polarizes more in response to an applied electric field than a material with low permittivity, thereby storing more energy in the material. In electrostatics, the permittivity plays an important role in determining the capacitance of a capacitor.

10.5.A.4 The permittivity of matter has a value different from that of free space that arises from the matter’s composition and arrangement.

• 10.5.A.4.i Within a given material, electric permittivity is determined by the ease at which electrons can change configurations within the material.

• 10.5.A.4.ii Conductors are materials within which charge carriers move easily through the material; insulators are materials within which charge carriers cannot move easily.