Solution to task 456 from Chertov´s for extramural stud

Solution to task 456 from Chertov´s for extramural stud

456. A flat circuit with a current I = 5 A is freely established in a uniform magnetic field (B = 0.4 T). Contour area S = 200 cm2. Keeping the current in the loop unchanged, it was rotated relative to the axis lying in the plane of the loop by an angle α = 40 °. Determine the work done by A.