Page 172 - Basic Electrical Engineering

Figure 2.74

2.8.3 Norton’s Theorem

We have seen earlier that in applying Thevenin’s theorem, a network is

converted into a voltage source and an equivalent series resistance connected
across two terminals of any resistance through which current has to be

calculated.
In applying Norton’s theorem, a network is converted into a constant

current source and a parallel resistance across the terminals of the resistance
through which current has to be calculated. The Norton’s theorem is stated as
follows:

Any two terminal networks consisting of voltage sources and resistances
can be converted into a constant current source and a parallel resistance.

The magnitude of the constant current is equal to the current which will flow
if the two terminals are short circuited and the parallel resistance is the
equivalent resistance of the whole network viewed from the open-circuited

terminals after all the voltage and current sources are replaced by their
internal resistances.

To understand the application of the theorem let us consider a simple
circuit as shown is Fig. 2.74.