1. The problem statement, all variables and given/known data Some light-dimmer switches use a variable resistor as shown in figure. The slide moves from position x = 0 to x = 1, and the resistance up to slide position x is proportional to x (the total resistance is Rpot = 100Ω at x = 1). What is the power expended in the light bulb if x = 0.5? 2. Relevant equations Rseries = R1 + R2 + ... Rparallel = 1 / (1 / R1 + 1 / R2 + ...) P = V2 / R = I2R 3. The attempt at a solution I tried first to obtain the total resistance, which is 50 + 1 / (1 / 50 + 1 / 205), and use this number to divide the voltage squared in order to get the power, but this is not correct. I don't know what I'm missing here. Any help will be appreciated.