Nortons Theorem
Nortons theorem is an analytical method used to change a complex circuit into a simple equivalent circuit consisting of a single resistance in parallel with a current sourceNortons Theorem states that “Any linear circuit containing several energy sources and resistances can be replaced by a single Constant Current generator in parallel with a Single Resistor“.
As far as the load resistance, RL is concerned this single resistance, RS is the value of the resistance looking back into the network with all the current sources open circuited and IS is the short circuit current at the output terminals as shown below.
Nortons equivalent circuit

For example, consider our now familiar circuit from the previous section.


with A-B Shorted Out


Find the Equivalent Resistance (Rs)

Nortons equivalent circuit





Nortons Theorem Summary
The basic procedure for solving a circuit using Nortons Theorem is as follows:- 1. Remove the load resistor RL or component concerned.
- 2. Find RS by shorting all voltage sources or by open circuiting all the current sources.
- 3. Find IS by placing a shorting link on the output terminals A and B.
- 4. Find the current flowing through the load resistor RL.