Nortonäquivalent

The Nortonäquivalent, commonly called the Norton equivalent, is a way to represent a linear electrical network by a single current source in parallel with a resistor, as seen from two output terminals. It is the dual counterpart of the Thevenin equivalent: both provide the same external behavior for any load connected to the terminals.

The Norton circuit consists of a current source In in parallel with a resistor Rn. The current In is the short-circuit current that would flow if the output terminals were directly connected by a conductor. The resistance Rn is the equivalent resistance seen at the terminals with all independent sources deactivated (voltage sources replaced by shorts and current sources opened). When dependent sources are present, they remain active during this resistance calculation.

Relation to Thevenin: any linear network with independent sources can be converted between Norton and Thevenin forms. If a network has a Thevenin equivalent Vth in series with Rth, the Norton equivalent is In = Vth / Rth in parallel with Rn = Rth. Both representations yield identical terminal voltages and currents for every possible load.

How to determine it: 1) find In by shorting the output and computing the resulting current. 2) find Rn by deactivating independent sources and calculating the equivalent resistance at the terminals (keeping dependent sources active). 3) optionally verify by computing Vth = In Rth and ensuring the load behavior matches with the Thevenin form.

Applications: the Norton model is convenient for analyzing networks with parallel current paths or multiple loads, and it simplifies current-driven load calculations and certain circuit transformations.