Norton's theorem
Known in Europe as the Mayer–Norton theorem, Norton's theorem holds, to illustrate in DC circuit theory terms, (see that image):
For AC systems the theorem can be applied to reactive impedances as well as resistances.
The Norton equivalent circuit is used to represent any network of linear sources and impedances at a given frequency.
Norton's theorem and its dual, Thévenin's theorem, are widely used for circuit analysis simplification and to study circuit's initial-condition and steady-state response.
Norton's theorem was independently derived in 1926 by Siemens & Halske researcher Hans Ferdinand Mayer (1895–1980) and Bell Labs engineer Edward Lawry Norton (1898–1983).
To find the equivalent,
This is equivalent to calculating the Thevenin resistance.
In the example, the total current Itotal is given by:
The current through the load is then, using the current divider rule:
And the equivalent resistance looking back into the circuit is:
So the equivalent circuit is a 3.75 mA current source in parallel with a 2 kΩ resistor.
A Norton equivalent circuit is related to the Thévenin equivalent by the equations:
The passive circuit equivalent of "Norton's theorem" in queuing theory is called the Chandy Herzog Woo theorem. In a reversible queueing system, it is often possible to replace an uninteresting subset of queues by a single (FCFS or PS) queue with an appropriately chosen service rate.
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