1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Find equivalent resistance in this circuit

  1. Feb 3, 2013 #1
    1. The problem statement, all variables and given/known data
    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


    User Avatar

    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


    User Avatar

    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


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    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.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook