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

The situation is shown in figure . The magnetic field at the site of dl , due to the first wire is ,
`B=(mu_(0)i_(1))/(2pil)`
This field is perpendicular to the plane of the figure going into it . The magnetic force on the length dl is . `dF=i_(2)dlBsin90^(@)`
This force is parallel to the current `i_(1)`.