1. The problem statement, all variables and given/known data If you accidentaly leave your car headlights (current drain 5A) on for one hour, how much of the 12-V battery's chemical enegy is used up? 2. Relevant equations Well, there's Ohm's Law...and it's million forms 3. The attempt at a solution First things first, I'm not sure whether to think of the power source as an ideal battery or not (ie, should I think about an internal resistance or not.) Ok, the time factor is throwing me off. I'm not sure how to use the time (one hour) in any form of Ohms law. And I'm not sure if the current drain is the current through the battery of the entire circuit or the headlights or what. Any ideas?