1. The problem statement, all variables and given/known data A battery supplies a steady current of 5.6 A for 21 s. During this time 1410 J of chemical energy is transformed into electric energy, but 560 J of this electric energy is transformed into heat energy inside the battery. What is the total power output of the battery? 2. Relevant equations P = E/t 3. The attempt at a solution What is confusing me is: is the energy I should consider in the "total power output" the energy associated with the emf - 1410 J - or the energy associated with the terminal voltage - 1410 J – 560 J = 850 J? I don't understand why I should use one or the other. The next question asks pretty much the same question but with emf and current, and doesn't even give a terminal voltage, so I am guessing I should use 1410 J, but I don't understand why this is. Could someone please help explain?