Electronic – Finding equivalent resistance

circuit analysis

The image shown right below is a schematic diagram of the circuit.

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There we need to find the equivalent resistance through X and Y.

I reduce the inner most resistors , because I figure out that there is a Wheatstone bridge out there, the resistance that I removed are shown below.

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How can I proceed further , I have no idea , I am stuck on this .How could I proceed further and find the equivalent resistance through X and Y ?

Best Answer

It's quite easy if you exploit the symmetry:

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Because of the radial symmetry the 5 marked nodes have the same potential. Therefore there will be no current going throught the 5 marked resistors, i.e. you can treat them as being absent.

So the final resistance will be (R + R / 2) / 5