[URL]http://en.wikipedia.org/wiki/File:Magnetischer_Kreis.svg[/URL] The attached image shows a magnetic circuit with a small air gap. The magnetic material on each side of the gap is attracted to the other side. I've seen the magnitude of the force calculated based on principle of virtual work from an energy gradient. My "problem" is I can't see the how the force arises in terms of the Lorentz equation. The amphere currents or electron spins are in the plane of the face of the magnetic material. The field is mostly perpendicular to the face. So in terms of the Lorentz equations how is the B field and currents oriented to get a force in a direction perpendicular to the face? My first though is because the B field is in reality not uniform across the gap. However the virtual work method (which seems the be very popular for this problem) starts off by assuming the field is uniform across the gap.