Solution to task 418 from Chertov´s for extramural stud

Solution to task 418 from Chertov´s for extramural stud

418. A thin conducting ring with a current I = 40 A is placed in a uniform magnetic field (B = 80 mT). The plane of the ring is perpendicular to the lines of magnetic induction. The radius R of the ring is 20 cm. Find the force F stretching the ring.