In Fig. 29-56, four long straight wires are perpendicular to the page, and their cross sections form ...

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In Fig. 29-56, four long straight wires are perpendicular to the page, and their cross sections form a square of edge length a = 6.65 cm. Each wire carries 18.7 A, and all the currents are out of the page. What is the magnitude of the net magnetic force per unit length on wire 1?