Halliday, Resnick & Walker — Magnetic Fields Due to Currents: Problem 26

26 In Fig. 29-41, a long circular pipe with outside radius \(R = 2.6 \text{ cm}\) carries a (uniformly distributed) current \(i_1 = 2.12 \text{ mA}\) into the page. A wire runs parallel to the pipe at a distance of \(3.00R\) from center to center. Find the (a) magnitude and (b) direction (into or out of the page) of the current in the wire such that the net magnetic field at point \(P\) has the same magnitude as the net magnetic field at the center of the pipe but is in the opposite direction.