Re: Why does an aluminium ring hover above an alternating electromagnet?

Hi John,

A changing magnetic field induces a ring current in conductors. The current
creates another magnetic field in the reverse direction to the original 
one. Two reverse magnetic fields repulse each other. Thus the ring hovers.
Superconductors hover even in a constant magnetic field, because they do 
not have any electrical resistance and the ring current induced by 
switching on the magnetic field flows forever.
I hope that makes it clearer. Apart from spooking audiences, the effect 
might one day be used for wheel-less vehicles (trains).

Greetings from Singapore,
    Frank