A region in which an electric charge experiences a force usually because of a distribution of other charges. The electric field strength or electric intensity (E) at any point in an electric field is defined as the force per unit charge experienced by a small charge placed at that point. This is equivalent to a potential gradient along the field and is measured in volts per metre. The strength of the field can alternatively be described by its electric displacement D. The ratio D/E for measurements in a vacuum is the electric constant ε0. In a substance the observed potential gradient is reduced by electron movement so that D/E appears to increase: the new ratio (ε) is called the permittivity of the substance. An electric field can be created by an isolated electric charge, in which case the field strength at a distance r from a point charge Q is given by E = Q/4πr2ε, where ε is the permittivity of the intervening medium (see Coulomb's law). An electric field can also be created by a changing magnetic field.
Subjects: Physics — Chemistry.