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Ohm's Law Question

  1. Jul 23, 2006 #1
    A battery charger is connected to a dead battery and delivers a current of 7.5 A for 3.5 hours, keeping the voltage across the battery terminals at 12 V in the process. How much energy is delivered to the battery?

    I'm not exactly sure what I am doing wrong. I understand that we have to use Ohm's Law in this question. So doing that, I took the given current, and converted it into the total number of coloumbs used over the 3.5 hours. I then calculated the resistance, and then I multiplied the total coloumbs by the resistance, and got joules (151,200). That's wrong, so I'm not sure where I went wrong.

    I'd appreciate any help. Thanks.
  2. jcsd
  3. Jul 23, 2006 #2
    use [tex] E = P \cdot t = U \cdot I \cdot t[/tex] with t in seconds.
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