Twelve wires each having resistance 2 are joined to form a cube. A battery of 6 V emf is joined across points a and c. The voltage difference between e and f is V. [figure]
1
b, d, e, g lie on the symmetry plane midway between a and c all at V= 62=3 V no current in b–e, d–g.
[figure]
Branch a–h–(e, g)–f–c: R=2+1+1+2=6
current = 66=1 A, divides equally: 0.5 A in e–f
Ve-Vf=0.5 2=1 V
Answer: 1
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