Equivalent resistance across a circuit made of 12 resistors

AI Thread Summary
To solve the circuit with 12 resistors, identifying symmetrical points is crucial, as it simplifies the analysis by indicating that certain resistors can be ignored. In a symmetrical configuration, the potential difference between points A and H results in no current through specific resistors, allowing for easier calculations of equivalent resistance using series and parallel combinations. The equivalent resistance was calculated as 3/4 R in both symmetrical and non-symmetrical cases. For non-symmetrical circuits, applying Kirchhoff's Law can help derive a system of equations to find the equivalent resistance. Understanding the balance in such circuits, like the Wheatstone bridge, is essential for practical applications.
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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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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.
 
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?
 
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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