Twelve resistors of resistance 1Ω are arranged in such a way that they form a cube, as shown in the image. Find the resistance between points A and B on the cube.
Just to make it more clear, all the resistors are of the same value
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By symmetry, the three vertices adjacent to A are equipotentials, and so can be coalesced. Similarly, the thee vertices adjacent to B are equipotentials, and so can be coalesced.
The resulting circuit consists of a series of three 1 Ω resistors in parallel, followed by six 1 Ω resistors in parallel, followed by three 1 Ω resistors in parallel, giving a total effective resistance of 3 1 + 6 1 + 3 1 = 6 5 Ω .