Coefficient of electric conductivity of some substances is studied; peculiarities of general character are outlined in the process of description. For generalizing of kinetic characteristics in solids the factors of reciprocity, determining the level of interband exchange and permitting to present kinetic characteristics of metals, semimetals, and semiconductors from one point of view, are introduced. Methodology of description, taking into account interband exchange and the presence of common electrons in the far–order of their interaction, is developed. In particular, analytical expressions for generalized electric conductivity coefficients, Hall coefficient and thermoelectric force, which permit to describe these characteristics in metals, semimetals, and semiconductors using unique formulas, are obtained. The peculiarities in the description of the coefficient of electric conductivity for unarranged structures and conductors of non–electronic type are outlined. Common approaches in the description of various liquids by means of defining of characteristic of effective charge by analogy with the description of free quasi–particles in solids by the method of effective mass are outlined. Effective charge of an arbitrary current carrier in liquids is determined by means of transference number, expressed through the ion radii and masses of charge carriers, and can be redefined up to change of charge sign.