Chapter 29, Problem 40AP

Two circular loops are parallel, coaxial, and almost in contact, with their centers 1.00 mm apart (Fig. P29.40). Each loop is 10.0 cm in radius. The top loop carries a clockwise current of I = 140 A. The bottom loop carries a counter-clockwise current of I = 140 A. (a) Calculate the magnetic force exerted by the bottom loop on the top loop. (b) Suppose a student thinks the first step in solving part (a) is to use Equation 29.7 to find the magnetic field created by one of the loops. How would you argue for or against this idea? (c) The upper loop has a mass of 0.021 0 kg. Calculate its acceleration, assuming the only forces acting on it are the force in part (a) and the gravitational force.

Figure P29.40