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Battery with internal resistor

  1. May 9, 2008 #1
    [SOLVED] Battery with internal resistor

    1. The problem statement, all variables and given/known data
    What is the current in a 8.25 ohm resistor connected to a battery that has a .21 ohm internal resistance when the potential drop across the terminals of the battery is 6V?


    2. Relevant equations
    [tex]R_{s}=R_{1}+R_{2}...[/tex]

    [tex]V=IR[/tex]

    3. The attempt at a solution
    So I believe that the internal resistor can just be considered being in series to the other resistor, allowing me to calculate the equivalent resistor. Then with that, using V=IR, I thought I was able to get the current flowing through the circuit. I got .70921 A
    Can someone correct my train of thought?
     
  2. jcsd
  3. May 9, 2008 #2

    Hootenanny

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    Note that the potential drop across the terminals includes the internal resistance of the battery. The internal resistance of a battery may be depicted thus,
    [​IMG]
    So the actual emf of the battery is the 6V plus the voltage drop across the internal resistance. Do you follow?

    Image courtesy of Hyperphysics
     
    Last edited: May 9, 2008
  4. May 9, 2008 #3
    Yes I do thank you for your help. Funny that you got the picture off hyperphysics, I was on there trying to read about this
     
  5. May 9, 2008 #4

    Hootenanny

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    No problem.
    Hyperphysics is an excellent general physics reference, I'm glad that you chose to look there rather than Wikipedia :rolleyes:
     
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