The results are given of approximate calculations of the relative permittivity εr of conductive unmagnetic materials (metals and alloys) for a special case when the of conductivity and displacement currents are equal in a homogeneous unmagnetic medium. The above mentioned materials are widely used in the electric power engineering and high-voltage pulse engineering in conditions when alternating (pulse) electric currents and electromagnetic fields (EMFs) with different peak-temporal parameters are acting on them. It is demonstrated that in the studied case the examined materials for low frequencies f0 of the current and EMF (at the frequencies about 102 Hz) within the range of very long electromagnetic waves (EW) are characterized by very high values of the electrophysical parameter εr (about 1015). For the very high frequencies f0 of the current and EMFs (at the frequencies about 51013 Hz) from the range of infrared radiation the indicated conducting materials are characterized by the εr values of the order of (102–104) and according to the electro-physical parameter εr they will approach to solid dielectrics and ferroelectrics.