There is an infinitely long straight thread carrying a charge with linear density `lambda = 0.40 muC//m`. Calculate the potentail difference between points `I` and 2 is removed `eta = 2.0` times farhter from the thread than point 1.

Explanation

We know from Gauss theorem that the electric field due to an infiniely long straight wire, at a perpicular distance `r` from it equals , `E_(r) = (lambda)/(2pi epsilon_(0) r)`, So, the work done is
`int_(1)^(2) E_(r) dr = int_(x)^(pi x) (lambda)/(2pi epsilon_(0) r) dr`
(where `x` is perpendicular distance from the thread by which point 1 is removed from it.) Hence `Delta varphi_(12) = (lambda)/(2pi epsilon_(0)) In eta`