Irodov Problem 3.47

Using the expression derived for in problem 3.40 and setting , we obtain the electric field due to a dipole oriented along the z-axis, at a distance z along the z-axis as,



Consider another dipole with strength p and direction along the z-axis, in this field at a distance l as shown in the Figure, with charges q and -q separated by a distance d. Thus,



The net force on this dipole will be,