# Max power delivered to variable resistor

1. Jun 1, 2008

### enian

1. The problem statement, all variables and given/known data
http://img126.imageshack.us/img126/6400/picex8.jpg

Determine the maximum power that can be delievered to the varaible resistor R in the circuit of Fig 4.139.

2. Relevant equations

3. The attempt at a solution

I am not sure how to handle this because the resistor is in that diamond structure. I need to find V thev and R thev Any advice or a hint to get started?

2. Jun 1, 2008

3. Jun 1, 2008

### Defennder

To find $$R_{th}$$, short the voltage source. That means drawing a vertical line connecting the blue nodes in your 2nd diagram. Then you must find the equivalent resistance between the red nodes. You have to redraw the circuit in order to solve it easily.

Next to find $$V_{th}$$, from the original diagram find the open circuit potential difference across the red nodes with the voltage source added back in. That would be the thevenin voltage. You can use nodal analysis to solve this. I got 30V for this. Once you got both, you can use the formulae for the maximum power theorem to get the answer.