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Terminal voltage and current

  1. Mar 28, 2007 #1
    A battery has a terminal voltage of 12.0 V when no current flows. Its internal resistance is 2.0 Ω. If a 1.7 Ω resistor is connected across the battery terminals, what is the terminal voltage and what is the current through the 1.7 Ω resistor?

    Can someone point me in the right direction?
    I know I have to use V = E - Ir because there is a internal resistance.
    But I am not sure how to start...

    Thanks in advance.
  2. jcsd
  3. Mar 28, 2007 #2


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    Treat the internal resistance as a series resistor, find the total circuit current.

    What is the voltage drop across the internal resistance? What do you think that will do to the terminal voltage?
  4. Mar 28, 2007 #3
    The terminal voltage is less than the emf because there is a voltage drop across the internal resistance.

    I am still confused.
    Last edited: Mar 28, 2007
  5. Mar 28, 2007 #4
    As said earlier treat internal resistance as a series resistor

    net resistance= R+r = 2+1.7

    current= E/R = 12/3.7

    terminal voltage = E - Ir
  6. Mar 28, 2007 #5
    thank you so much!
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