Halliday, Resnick & Walker — Magnetic Fields: Problem 26

26 In Fig. 28-32, a rectangular loop carrying current lies in the plane of a uniform magnetic field of magnitude 0.050 T. The loop consists of a single turn of flexible conducting wire that is wrapped around a flexible mount such that the dimensions of the rectangle can be changed. (The total length of the wire is not changed.) As edge length x is varied from approximately zero to its maximum value of approximately 4.0 cm, the magnitude \(\tau\) of the torque on the loop changes. The maximum value of \(\tau\) is \(4.80 \times 10^{-8} \text{ N}\cdot\text{m}\). What is the current in the loop?