1. The problem statement, all variables and given/known data While going through a basic electrical engineering overview, I came across the equation U = QV, which is defined to be electrical energy. For Power, which is explained in the next section, P is basically the derivative of U = QV. I tried following the derivation myself, but for some reason, what I got was different from the book. 2. Relevant equations U= QV q = -1.6x10^-19 Coulombs ( basically a constant) The derivative of this turned out to be d/dt = V*d[Q]/dt. My question is HOW. 3. The attempt at a solution P = d/dt = Q * d[v]/dt; treated Q as a constant, but this doesn't line up. My Calculus must be rusty. Anyway, the full statement from the book: P = U'= V*Q' = VI= v^2/R = I^2*R -Thanks.