Two long wires, carrying currents ` i_1 and i_2,` are placed perpendicular to each other in such a way that they just avoid a contact. Find the magnetic force on a small length dl of the second wire situated at a distance l from the first wire. (figure)

Explanation

Solution: The situation is shown in figure(35- W5). The
magnetic field at the site of dl, due to the first wire is,
` B= (((mu_0)(i_1))/ 2 pi l).`
` This field is perpendicular to the plane of the figure`
`going into it. The magnetic force on the length dl is,`
` dF= (i_2)dl B sin 90^@ `
` = ((mu_0)(i_1)(i_2)dl)/(2 pi l)`
` This force is parallel to the current (i_1).