1. The problem statement, all variables and given/known data Calculate the total power generated by G 2. Relevant equations P=VI 3. The attempt at a solution I used the P=VI formula to calculate the total power generated by G which is 40W, and the answer turns out to be correct. But actually, I don't quite understand this topic of opposing emf. Like, why I can't I use the formula of P= V2/R instead? Why can't I get the same answer? For when using this equation, I know that I musn't include the value of 0.5Ω, which is the internal resistance of G. But why can't I get the same answer? Same goes for P=I2R. These three formulas all give 3 different answers, though I thought they are supposed to give the same value of P. What is wrong with my understanding?