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Homework Help: Equivalent resistance across a circuit made of 12 resistors

  1. Sep 28, 2010 #1
    hey can anybody please tell me how to solve this circuit?? :confused:

    I tried this sum out but I can't understand which points are symmetrical and have same potential..or how the current is distributed
     

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    Last edited: Sep 28, 2010
  2. jcsd
  3. Sep 28, 2010 #2
    The symmetry means that potential at C=D=E=F = 0.5 the pd between A and H
    This means there is no current through the arms CD and FG. So you can ignore the 2 resistors there.
    This allows you to simplify the circuit using series and parallel resistors.
     
  4. Sep 29, 2010 #3
    ok, I solved the combinations and I got 3/4 R.
    but what if the circuit is not symmetrical..that is if we have to find the equivalent resistance between A and B?
     
  5. Sep 29, 2010 #4
    I also get 3/4 R.
    If the circuit is not balanced, I can't see much use for it! Usually, these "bridge" type circuits are only useful when balanced. [eg Wheatstone bridge]

    To attempt to answer the question, though, one possibility would be to set up a system of Kirchhoff's Law equations for the various closed loops (where ΣIR = 0) as well as the main circuit supplying the pd that provides the main current.
    You would get 6 equations with 6 unknowns and a relationship between the main current and the applied pd. This would give the equivalent R.
     
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