A hollow cylinder of specific resistance `rho`, inner radius `R`, outer radius `2R` and length 1 is as shown in figure. What is the net resistance between the inner and outer surfaces?

Explanation

Consider a ring of width `dr` and radius `r`
Resistance across the ring is
`dR=(rhodr)/(dA)=(rhodr)/(2pirl)`
Net resistance `=int_(R)^(2R)(rho(dr))/((2pirl))=((rho)/(2pil))ln(2)`