Chapter 28, Problem 20P

(II) Repeat Problem 19 if the wire at x = 0 carries twice the current (2I) as the other wire, and in the opposite direction.

19. (II) Let two long parallel wires, a distance d apart, carry equal currents I in the same direction. One wire is at x = 0, the other at x = d, Fig. 28–38. Determine $\stackrel{\to }{B}$ along the x axis between the wires as a function of x.

FIGURE 28–38 Problems 19 and 20.