일반물리학 2 — Magnetic Fields Due to Currents: Problem 6

6 In Fig. 29-27, part of a long insulated wire carrying current $i = 5.78 \text{ mA}$ is bent into a circular section of radius $R = 1.54 \text{ cm}$. In unit-vector notation, what is the magnetic field at the center of curvature $C$ if the circular section (a) lies in the plane of the page as shown and (b) is perpendicular to the plane of the page after being rotated $90^{\circ}$ counterclockwise as indicated?