Parameter Sweep

[3rdDegreeBurns]

I'm trying to use a Parameter sweep to find the value of the unknow resistor (R 'knot') at its maximum power. I know from the equation solution that it should be 10 ohms, but when I run it i consistently get 1.5 ohms along with another one of my friends. I can't figure out what we're doing wrong! The question and schematic are as follows:

[Tien_P]

Hi,

Have a look at the attached circuit to see how you can sweep Ro resistance and for and output Ro power, I am not sure what the current and voltage source is for so I'll leave them out. 

I am sweeping Ro from 0 - 50 ohm at 1 ohm increment and I am using DC operating point as the base analysis, and under the output tab I lam ooking at the power dissipated by R0.