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Homework Help: Multiloop circuit: find equivalent resistance

  1. Jun 9, 2012 #1
    1. The problem statement, all variables and given/known data
    Find equivalent resistance in this circuit. (picture is in the attached files section)

    2. Relevant equations
    Series: Req=R1+ R2. . .

    Parallel: 1/Req = 1/R1 + 1/R2 . . .

    3. The attempt at a solution
    It seems to me that the 2nd 2ohm resistor (the one thats pointed vertically) has 2 different currents going through it in opposite directions. I also think that the 2nd 2ohm resistor is in parallel with both the 3ohm and 4ohm resisistors. The first 2ohm resistor also seems to be parallel with the other three resistors. So if I redrew the circuit I would say that all 4 resistors ultimately all have a parallel relationship to each other, but I'm really not sure?

    Attached Files:

  2. jcsd
  3. Jun 9, 2012 #2
    Use delta-star configuration conversion.
  4. Jun 10, 2012 #3
    Hi sonic91!! welcome to PF!! :smile:

    I don't think they are all in parallel. Also, the 2nd 2 ohm resistor cannot have two opposite currents passing through it. Nothing can...

    Try assuming the current in the circuit to be I, and voltage of the battery V(make an imaginary battery circuit). See how the electric current is distributed among the loops and make sure if I current is entering the system, I current should finally go out. :wink:

    Then use Kirchoff's Voltage Law for appropriate loops.

    Or, use delta-star transformation.
  5. Jun 10, 2012 #4


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    Homework Helper

    No, they are not. Remember, both terminals of parallel resistors are common with the other one. You have a pair of resistors which both terminals common. Which ones?
    Note, those terminals which are connected by a wire are considered "common".
    Look at the picture. You can shrink the wire on the left and turn the first 2 ohm resistor downward.


    Attached Files:

  6. Jun 10, 2012 #5
    Thanks for the help I think I've got it down now.
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