I have two toroidal permanent magnets which are fitted over
magnet.jpg (151.11 kB . 805x989 - viewed 4898 times)
magnet.jpg (151.11 kB . 805x989 - viewed 4898 times)a plastic tube with like poles facing each other.
Because of the magnetic repulsion the top magnet 'hovers' 20mm above the bottom one. I have had this pair
of magnets as an ornament in my workshop for more than 10 years and there is no discernable change in the
gap between them. The magnets are about 85mm in diameter, the central hole of the toroid about 50mm and they
weigh about 400g each.

My question is:
Where does the energy come from to support the top magnet against the force of gravity. Classical Physics seems to say that with the magnets in this static situation then no energy is involved and no work is done as
there is no movement or displacement. However, If I push the top magnet towards the lower one and release it, it
returns to it's 'hover' position. Clearly energy is required to do that. No matter how many times that is done, the permanent magnetism does not seem to be depleted.

As a thought experiment, if the bottom magnet was replaced with an electromagnet then electrical energy would be required to support the top magnet and if the power was removed the top magnet would drop. I realise that toroidal electromagnets have no external magnetic field but if bar magnets were used instead and constrained horizontally in a tube then the same would apply.