# Circuits Question: Thevenin Equivalent

• Engineering

## Homework Statement

Find thevenin equivelent of this circuit with respect to a and b Mesh Currents

## The Attempt at a Solution

Here I will try to find V(open circuit) = Vth = Vab ((I think this anyways))

I apply mesh currents (any faster methods are welcome if you know them) iA: -100/V/ + 10/ohm/(iA) + 40/ohm/(iA-iB)=0
iB: 40/ohm/(iB-iA) + 50/ohm/(iB-iC)=0
iC: 50/ohm/(iC-iB) + 20/ohm/(iC) + 200/ohm/(Ix) = 0
iD:-10/A/
iX: iX=iB-Ic

I get the folowing values using solve function on calculator:
iX=-40A/
iA=210/A/
iB=260/A/
iC=300/A/
iD=-10/A/

And using ohms law with parallel resistors having equal voltages..
Vab = 40/ohm/*(iA-iB) = -2000 = Voc = Vth

Now is where I begin to have trouble finding Isc...

I draw the short circuit between a and b (which I believe causes R3 and R4 to have no current through them thus making Ix = 0 and vs2 = 0 as well): Simplifying it you gain ((if my previous assumptions are correct reguarding the short circuit)): Now from here I am actually unsure what I should do. I do want to do mesh currents but I dont know if I will recieve a correct answer. I also wondered if I could use a closed surface... something like this perhaps: If I used that I would get an equation like -100/V/ / 10/Ohms/ + Isc = 0

But then again it just doesnt seem quiet right to me. And i have no way to check my answer.