Find the magnitude and direction of a force vector acting on a unit length of a thin wire, carrying a current I = 8.0 A, at a point O, if the wire is bent as shown in
(a) Fig. 3.68a, with curvature radius R = 10 cm;
(b) Fig. 3.68b, the distance between the long parallel segments of the wire being equal to l = 20 cm.