According to Thevenin's theorem a two terminal power supply can be represented like this:

And According to Norton's theorem the same power supply can be represented like this:

From the Thevenin circuit we have

I_{L}= V_{T}/(R_{int}+R_{L})

From the Norton circuit we have

V_{AB}= I_{SC}(R_{int}R_{L}/(R_{int}+R_{L})) = I_{L}R_{L}I_{L}R_{L}= I_{SC}(R_{int}R_{L}/(R_{int}+R_{L})) I_{L}= V_{AB}/R_{L}= I_{SC}R_{int}/(R_{int}+R_{L})

V_{AB} is the same for both circuits, so
we can substitute what we stated I_{L} was for the Thevenin circuit:

I_{SC}R_{int}/(R_{int}+R_{L}) = V_{T}/(R_{int}+R_{L}) I_{SC}R_{int}= V_{T}

Both theorems give us a way to represent complicated circuits as simpler ones, either as a simple series circuit, or a simple parallel circuit.

Fischer-Cripps. A.C., *The Electronics Companion.* Institute of Physics, 2005.

Copyright © 2014 Barry Watson. All rights reserved.