The current-carrying wire loop in Fig. lies all in one plane and consists of a semicircle of radius 10.0 cm, a smaller semicircle with the same center, and two radial lengths. The smaller semicircle is rotated out of that plane by angle u, until it is perpendicular to the plane (Fig. 29-60b). Figure 29-60c gives the magnitude of the net magnetic field at the center of curvature versus angle u. The vertical scale is set by Ba = 10.0 μT and Bb = 12.0 μT. What is the radius of the smaller semicircle?

2a (I Bi et 50 Ba t/4 (rad) /2