Abstract. Diamagnetic objects are repelled by magnetic
fields. If the fields are strong enough, this repulsion can
balance gravity, and objects levitated in this way can be held
in stable equilibrium, apparently violating Earnshaw’s
theorem. In fact Earnshaw’s theorem does not apply to
induced magnetism, and it is possible for the total energy
(gravitational + magnetic) to possess a minimum. General
stability conditions are derived, and it is shown that stable
zones always exist on the axis of a field with rotational
symmetry, and include the inflection point of the magnitude
of the field. For the field inside a solenoid, the zone is
calculated in detail; if the solenoid is long, the zone is
centred on the top end, and its vertical extent is about half
the radius of the solenoid. The theory explains recent
experiments by Geim et al, in which ** a variety of objects (one
of which was a living frog) was levitated **in a field of about
16 T. Similar ideas explain the stability of a spinning magnet
(LevitronTM) above a magnetized base plate. Stable levitation
of paramagnets is impossible.
bstix@feddit.dk 1 year ago
In gonna save y’all from downloading a pdf.