How Much Energy Does Leaving Car Headlights On Drain from a 12V Battery?

[Seda]

Homework Statement

If you accidentaly leave your car headlights (current drain 5A) on for one hour, how much of the 12-V battery's chemical energy is used up?

Homework Equations

Well, there's Ohm's Law...and it's million forms

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?

 

[berkeman]

What is the definition of electrical power in terms of voltage and current? What is the definition of energy, in terms of power and time duration...?