Abstract
A model is presented which allows the conductivity due to hopping between randomly distributed localized states to be calculated for any form of density of states This model has been applied analytically to the case of a flat density of states, and produces the Mott 1/T 1/4 relation at low temperatures, if the applied electric field is sufficiently low. The field-dependence of the conductivity is found to be log [sgrave] ∼ F 2 at low fields, and log [sgrave] ∼ 1/F 1/4 at very high fields.