Thevenin resistance

Thread Starter


Joined Nov 10, 2017
I Am working on finding the thevenin. Resistance in this circuit. Here are my best three attempts. I am Just confused if should work away from the source or to the source or to the load?



Joined Mar 31, 2012
None of your answers are correct, though one of your equations is getting close.

Usually, the best first step in finding the Thevenin equivalent is to redraw the circuit with the load resistor removed (and replaced with two terminals) and the terminals placed on either the right or the left of the circuit. To find the Thevenin resistance (assuming no dependent sources), replace all voltage sources with a short circuit and all current sources with an open circuit.

Do that and see what you get.

An alternative (which works even with dependent sources) is to simply analyze the circuit under two conditions.

Replace the load with an open circuit and find the voltage across the load terminals. That's the Thevenin voltage.

Replace the load with a short circuit and find the current through the load terminals. That's the Norton current.

The equivalent resistance is the ratio of the Thevenin voltage to the Norton current (being sure to take the proper polarities into account because the equivalent resistance CAN be negative).