Put the child in the carrousel not in the center, since it won’t be fun there for the child ;-)) and make it hold a bar magnet and an electrically charged ball. The electrons around a nucleus have a certain intrinsic dipole moment, hence the bar magnet, and a charge moving circularly wil also create a dipole moment. Both can then be measured by the magnetometer in the centre of the carrousel. Only the contribution of electrons in the nucleus is not present in this analogy.