A wire of resistance 4R is bent in the form of a circle. What is the effective resistance between the ends of the diameter?

Explanation

Resistance of log wire = 4R
Hence the resistance of half wire =
`(4 R)/(2) = 2R`

Now these two wire are connected in parallel. Hence the effective resistance between the ends of the diameter
`R_(P) = (R_(1) R_(2))/(R_(1) + R_(2)) implies R_(rho) = (2R xx 2R)/(2R + 2R)`
`:. R_(rho) = R`.