Twelve identical resistances arranged on all edges of a cube. The resistors are all the same. Then find the equivalent resistance between the edges A and B as shown in figure.

Explanation

(a) All resistances are `R`
`B, D, E` are at the same potential
`C , F, H` are at the same potential
Make new diagram by placeing `B , D, E` at one place and `C, F, H` at another place.
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(b)All resistance are `R`
`B , D` are at the same potential
`F, H` are at the same potential
Make new diagram by placing `B` and `D` at one place and `F` and `H` at another place and then solve.
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( c) `D` and `E` are at the same potential
`C` and `F` are at the same potential
Make new diagram by placing `D` and `E` at one place and C and `F` at another place.
.