A long, straight wire carries a current i. Let `B_1 be the magnetic field at a point P at a distance d from the wire. Consider a section of length l of this wire such that the point P lies on a perpendicular bisector of the section. Let B_2 be the magnetic field at this point due to this section only. Find the value of d/l so that B_2 differs from B_1 by 1 %.

Explanation

`B_1 =(um_oi)/(2pid)`and `
`. `B_2 = (mu_oil)/(4pi d^2)xx(2)/sqrt 2`
`. Given `B_2 - B_1 = B_1xx (1)/(100)`
`. `rArr (sqrt mu_oil)/(4pid^2) = (1.01) (mu_oi)/(2pid)`
`. `(d)/(l) = (1.414)/(2.02) = 0.7` .