Wires 1 and 2 carrying currents i1 and i2 respectively are inclined at an angle θ to each other. What is the force on a small element dl of wire 2 at a distance of r from wire 1 (as shown in figure) due to the magnetic field of wire1
Length of the component dl which is parallel to wire(1) is dl cosθ, so force on it.
F=μ04π.2i1i2r(dl cosθ)=μ0i1i2dl cosθ2πr