Abstract
The influence of the plasticiser DOP on electric conduction and dielectric relaxation in polyvinyl chloride has been investigated. The results were explained in terms of the compensation law between the pre-exponential factor of an Arrhenius equation and its activation energy. This compensation law has been observed not only in electric conductivity and dielectric relaxation but also in mobility and carrier density. The basis for the compensation law has also been discussed theoretically from a thermal expansion point of view.