I'm having trouble understanding the concept of a problem I have for homework. The problem has a circuit with a variable resistor, and the resistor is adjusted until the power dissipated is 250w. I'm supposed to find multiple values of the resistance that can equal 250w, but I'm having trouble understanding how. Heres the actual question: The variable resistor in the circuit is adjusted until the power dissipated in the resistor is 250 W. Find the values of R that satisfy this condition. Here's a picture of the circuit: This question is from a section introducing the Maximum Power Transfer. I was thinking maybe finding the Thevenin Equivalent excluding the variable resistor R, and then use the resistor R to act as a load to the Thevenin circuit. With the circuit reduced, stating the maximum power would be = 250 W (and in this case Rth = R for a maximum value), but the Rth I found is not correct according to the book. I'm not sure if I'm approaching this right or not. I don't need an answer, just a general direction of how to solve it. Any help is appreciated.