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Find equivalent resistance in this circuit

  1. Feb 3, 2013 #1
    1. The problem statement, all variables and given/known data
    http://session.masteringengineering.com/problemAsset/1515645/4/Steif.ch02.p28.jpg
    Find the equivalent resistance between node A and B, knowing that Rab = Vab/Iab

    2. Relevant equations
    KCL and KVL, I know.


    3. The attempt at a solution
    There is nothing in series or parallel here, so what I did is set up KCL equations and KVL loop equations (top and bottom loops), so 6 equations with 6 unknowns and I can find Iab. I don't know how to find Vab though...
     
  2. jcsd
  3. Feb 3, 2013 #2

    gneill

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    Staff: Mentor

    You don't find Vab, you stick a voltage source there (value of your choosing, or just leave it as a variable, "Vab"). The equivalent resistance Rab is given by the ratio Vab/Iab.

    Presumably the Vab variable will cancel out in the workings leaving you with an expression for Rab in terms of R alone.
     
  4. Feb 3, 2013 #3
    I'm still confused though, is my method of finding Iab correct?
     
  5. Feb 3, 2013 #4

    gneill

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    Staff: Mentor

    Well, the approach of finding Iab given a source voltage Vab is correct. But you haven't shown the details of your work so it's not possible to say more.
     
  6. Feb 4, 2013 #5

    CWatters

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    Science Advisor
    Homework Helper

    You don't need to solve the equations to find Iab or Vab their own.

    Rab = Vab/Iab

    so reaarange the equations until you get one for the ratio Vab/Iab in terms of the resistors only.
     
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