Thermal conductivity is a measure of a material's ability to transfer heat through itself. To transfer heat rapidly or to prevent heat transfer, higher thermal conductivities or low thermal conductivities materials respectively must be used. Knowledge of heat transfer is of important to control heat addition or heat removal processes. Many techniques have been used to determine thermal conductivity such as guarded hot plate, Lee's disc, laser flash...etc., methods. The physics of dielectric deals with the properties of the dielectrics such as dielectric constant( permittivity), loss factor, tanδ, ...etc. , and the dependence of these properties on the material's structure and on external factors such as temperature, frequency of the applied field, radiation, humidity,...etc.