Chapter 8, Problem 8.8P

Two conducting strips, having infinite length in the z direction, lie in the xz plane. One occupies the region d/2 and carries surface current density K = K°a_z ;the other is situated at -( b + d/2) < x < -d/2 and carries surface current density - K₀a_z. (a) Find the force per unit length in z that tends to separate the two strips, (b) Let b approach zero while maintaining constant current, I = K₀b, and show that the force per unit length approaches đ�œ‡₀I²/(2đ�œ‹d) N/m.a