# Homework Help: Thevenin equivalent circuit help

1. Jan 5, 2012

### full123

http://img855.imageshack.us/img855/5369/eehmwk.jpg [Broken]

I haven't done this before with 2 voltage sources so I'm not sure how I would go about doing it.

If someone could show me step by step how to understand this, I would appreciate it.

Equivalent resistance = 2.5ohms, right?
But what about Vs?

Last edited by a moderator: May 5, 2017
2. Jan 5, 2012

### Staff: Mentor

There are several different ways to solve this circuit. What circuit theorems have you been introduced to?

Last edited by a moderator: May 5, 2017
3. Jan 5, 2012

### Staff: Mentor

Can you determine the voltage between a and b on the main circuit? That becomes Vs in the Thevenin equivalent.

4. Jan 6, 2012

### Su3liminal

2 or 3 voltages, it doesn't matter. It is the same approach most of the time
Find the voltage across AB, that is: Vab (using nodal analysis). Then find the short-circuit current Isc, that is in the direction of the voltage DROP across AB (using mesh current method). Then it is a matter of using Ohm's law to find Rth and constructing Thevenin equivalent circuit.
Of course you don't have to have to find the current Isc (which is cumbersome used often), since you can replace the Voltage sources by short circuits and then find the equivalent resistance Rth. But I was just suggesting to use the formal approach.

Last edited: Jan 6, 2012