1. The problem statement, all variables and given/known data Or is it only valid in vacuum condition? Segment of straight wire carrying current I (at distance r) dB = u.Idl x r / 4pi . r^2 (I've came across it on a book about Maxwell's Equations.) 2. Relevant equations 3. The attempt at a solution Does correction have to be made for polarization or magnetization of the material medium? If so, how?