Only qualitative aspects on the skin effect in conductors are properly described in the technical literature on power systems applications. Although the qualitative analysis is an important issue, it is not sufficient for a full approach and proper understanding of this electromagnetic phenomenon in power systems, more specifically in power transmission systems. The present work intends to provide a quantitative analysis of the skin effect on conductors based exclusively on the Maxwell Equations, whereby both physical and mathematical treatments of the phenomenon are properly analysed. This approach contrasts with the traditional one that uses a complex formulation based on both the differential Maxwell equations and potential concepts. Finally, a discussion on the application of the Poynting theorem on the external surface of the cylindrical conductor is presented in order to evaluate not only the resistance, but also the inductance as a function of the frequency, which is not properly discussed in the technical literature on power systems.