Let us conclude this chapter by returning to one of the more striking puzzles we faced when making the observations at the beginning of Chapter 22. There you found that charged objects of either sign exert forces on neutral objects, such as when a comb used to brush your hair picks up pieces of paper. Our qualitative understanding of the polarization force was that it required two steps:
The charge polarizes the neutral object, creating an induced electric dipole.
The charge then exerts an attractive force on the near end of the dipole that is slightly stronger than the repulsive force on the far end.
We are now in a position to make that understanding more quantitative.