Origins of the Equivalent Circuit Concept

The equivalent circuit concept derives from the Superposition Principle and Ohm’s Law. Two forms of the equivalent circuit, the Thévenin equivalent and the Norton equivalent, distill any linear circuit into a source and an impedance. The development of these equivalents spans almost seventyfive years, with others than the eponymous people assuming equally important roles. This report describes the pertinent biographies of Helmholtz, Thévenin, Mayer, and Norton, and provides the relevant sections from their original papers on equivalent circuits.