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Homework Help: Variable resistor graph

  1. Mar 12, 2010 #1
    1. The problem statement, all variables and given/known data
    A variable resistor, R, is connected to the terminals of a battery (dashed box in the diagram). The graph below shows data collected in the circuit as R is varied. What is V0, in volts?

    What is the internal resistance, r, in ohms?

    should the V0 be measured at the top of the line where it is at the smallest current? because that is what the TA explained to do, I tried and I can't seem to get it right
     

    Attached Files:

  2. jcsd
  3. Mar 12, 2010 #2
    Did you extend the line backwards to where I=0(where it cuts the y axis)
     
  4. Mar 12, 2010 #3

    berkeman

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    Staff: Mentor

    And adding one more question to Dadface's post, what is special about where it cuts the y axis?
     
  5. Mar 12, 2010 #4
    that worked! thanks
     
  6. Mar 12, 2010 #5

    berkeman

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    But why did it work. Do you understand that part?
     
  7. Mar 12, 2010 #6
    Because V0 should be at lowest current (ie when it is 0) but the internal resistance keeps it from actually getting there?
     
  8. Mar 12, 2010 #7

    berkeman

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    Staff: Mentor

    That part is correct. V0 is the "open circuit voltage", so when no current is flowing. The other thing you can use to figure out the internal resistance is the "short circuit current". Once you have V0 and Rs, you have characterized your voltage source.
     
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