This book offers a progressive, operational overview of electrokinetics: from charge carriers (electrons, holes, ions, plasma) to the macroscopic laws that govern real circuits. After reviewing the fundamental quantities (current, current density, electric field) and energy balances (Joule effect, power, efficiency), the text bridges the gap between the microscopic and macroscopic forms of Ohm's law, while clarifying the role of resistivity, conductivity and mobility. Kirchhoff's laws are treated systematically (nodes, meshes, direction of travel), then applied to the analysis of...