Source Transformations: Find Vth & Rth

[jdawg]

Homework Statement

Find the thevenin equivalent circuit by performing source transformations only.

Homework Equations

The Attempt at a Solution

Answers: Vth=60v and Rth=30.
I managed to get Rth correct, but I'm not sure if everything I did was "legal". I can't seem to find Vth.

 

[cnh1995]

Homework Statement

Find the thevenin equivalent circuit by performing source transformations only.

Homework Equations

The Attempt at a Solution

Answers: Vth=60v and Rth=30.
I managed to get Rth correct, but I'm not sure if everything I did was "legal". I can't seem to find Vth.

In the 3rd circuit, your transformation of V into I is wrong since the resistor and current source(transformed) are not in parallel. But you don't need a 3rd step. I think in the 2nd circuit itself, the answer is obvious (60V).

 

[gneill]

Your third step is incorrect. When a voltage source is transformed into a current source the associated resistor must end up in parallel with the current source. Also, you should work from one end of the circuit to the other, towards the output, in stages.

Your first step, converting the 4 A source to a 40 V source allowed you to "swallow up" one 10 Ω resistor. The logical next step would be to convert this "new" voltage source and resistance back to a current source allowing you to "swallow up" more of the circuit with simple parallel or series combinations. Don't be afraid to convert back and forth between source types if it allows you to make progress in reducing the circuit.

 

[jdawg]

Thanks, I'll try reworking it!