How does a copper ring levitates above a AC supply primary coil? Doesn't AC current gives decreasing current and so decreasing magnetic fields or flux. This should then attract the copper ring above primary coil. When magnitude of current increases in AC then due to Lentz law as we know ring will get repelled. But what about the decrease of current. Dosen't current decreases like it increases in AC. What is the reason of that lift. Even when anyone blocks ring at a place it still try to lift.   Why???  I am very confused on that topic. I am trying to find it hard from everywhere and thinking myself too. But it seems like how?why? Why only lift above?
 A: I was wrong in my first answer. It is slightly more subtle than I thought.
Perhaps it has to do with the shape of the exciting field and its oscillation frequency.
If the field diminishes quickly (spatially) with the distance to the exciting coil (e.g. if the field diverges strongly), the second coil could be in the air during the attracting phase, so that it might not see said "attractive phase" as strongly as he felt the repulsive phase.
If the frequency of the oscillator, the shape of the field, and the mass of the second coil (the ring), are right, and the attractive phase always coincides with the ring being in the air, then it could work.
So, if I have got it right this time, it means that it is not a purely electromagnetic problem, but that is also has a mechanical aspect.
One can picture it naively as the exciting field "joggling" with the second coil (the way a ping-pong player bounced a ball with a paddle).
A: Besides the bad English, I think what you're referring to is the jumping ring experiment, which is a demonstration of Faraday's laws of electromagnetic induction and also of Lenz's law. You can read more about it here.
