Electricity, Magnetism and Electromagnetism, Ch Ampère's law, magnetic flux and the shape of the magnetic field
Problem
Two long straight parallel wires run perpendicular to the page and carry steady currents: wire A carries 7.0A out of the page and wire B carries 3.0A into the page. A closed loop drawn in the plane of the page encircles both wires once and is traversed anticlockwise, so that by the right-hand rule its positive normal points out of the page.
((a)) Find the circulation ∮B⋅dl of the magnetic field round this loop.
((b)) Elsewhere, a flat square coil of 250 turns and side 4.0cm sits in a uniform magnetic field of magnitude 45mT, with the normal to the coil's plane at 30∘ to the field. Find the magnetic flux through one turn.
((c)) Find the flux linkage NΦB of that coil.