Non-uniform distribution of electric current density in a conductor, attributable to electric currents in the neighbouring conductors, is referred to as proximity effect. The term proximity effect only expresses the qualitative description of reality. The subject of the article is an analysis of induced voltage and current in a segment of a loop formed by two long parallel conductors of arbitrary cross section connected to a source (transmission line) and in the equivalent circuit of the loop segment, which is a series RL circuit. The original contribution of the article is an analysis of the definitions of self-inductance coefficients, which characterize an inductor, and determine the voltage induced on the inductor and the current in the equivalent RL circuit. It is shown that the calculation of induced voltage and current in terms of self-inductance coefficients is in principle inaccurate, in particular when the proximity effect applies.