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## Homework Statement

Find resistance R so that maximum power is transferred to this resistor.

http://i.imgur.com/XsxTFCq.png

## Homework Equations

Rth = Voc/Isc

## The Attempt at a Solution

I tried to find the Thevenin equivalent circuit across the resistor R because the Thevenin resistance must be equal to the load resistor in order for maximum power to be transferred.

I replaced R with an open circuit to find the open circuit voltage.

Using Nodal Analysis, I obtained the equation: (V1 - 4V)/5 + V1/15 = 0

So, V1 = 3 = Voc.

Then I redrew the circuit and replaced R with a short circuit and solved for two voltages at the nodes.

http://i.imgur.com/247x27x.png

I used Nodal Analysis and obtained two equations.

[3Vx = V2/6]

(V1-4V)/5 + V1/15 + V2/2 + (V1-V2)/5 = 0

V2/6 + (V2-V1)/5 = 3V2/6

I got V1 = 48V, V2 = -72V and Isc = V2/6 = -12A

so I got Rth = 3/-12 = -0.25 ohms.

This isn't right, but I"m not sure what I did wrong.