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Homework Help: Electric Circuits Problem

  1. Mar 20, 2008 #1
    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?
  2. jcsd
  3. Mar 20, 2008 #2


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    Staff: Mentor

    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...?
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