1. The problem statement, all variables and given/known data an infinite wire carries current into the paper as shown. (see attach.) compute [integral(B dI)] along the closed path indicated 2. Relevant equations electric potential V = IR where I is current, R is resistance magnetic field B = mu_0(I)/2pi(r) = mu_0(I)/dr where mu_0 is constant = 4pi*10^-7, r is radius, I is current, dr is change in radius 3. The attempt at a solution the path is basically a part of a small inner circle of radius r_1, and 'part' of a larger circle of radius r_2. to find the change in radius dr, i need to find the path which equals r_net ( see 2nd attach). does the fact that the current is carried into the paper just affect the sign of the current? or does it have a greater affect? i'm not sure whether dr = path length, if it is not, to find dr am i supposed to just do (r_2 - r_1 = dr)? how do i determine change in current I, dI? am i missing the correct equation?