If I place a magnet near a carrousel, a field will be created and interact with a nucleus that exists at the center. This is the dipolar term. Now imagine that a random kid (his unexpected behavior will resemble the probabilistic nature of electrons) picks up the charged ball and takes it with him on the carrousel. This orbital movement will be the orbital term. Finally, the kid might snick in with the ball inside the carrousel and go near the nucleus at the center. That will be the Fermi term. In addition, I guess that we could use the magnetometer to measure the fields in the different cases, but I am not sure.