The nucleus can be imitated by placing the magnetometer on the rotational axis of the carousel. The child (that is riding one of the horses) then represents an electron orbiting the nucleus. The child is holding the bar magnet and the electrically charged ball. The electrically charged ball will then orbit the magnetometer, and thus there will be a loop current. This is analoguous to the orbital term. The bar magnet represents the spin of the electron and will result in the dipole term. I have no idea how to represent the Fermi term