What are the magnetic properties of cast aluminum in an AC magnetic field? In grade 10 I put a sand cast, aluminum, Indian head ashtray over an electromagnet made from several pieces of iron flat bar, insulated and wrapped with coils of #14 varnished copper wire plunged directly into a 120v 60 cycle outlet. Initialy it hoped of the poleface of the magnet, so with some containment I tried again. This time it lifted aprox. 1.5" of the poleface with no axil rotation, where it remained as long as the magnet was plugged in. I would appreciate reading suggestions or direction on this topic. Thank you
 A: The electromagnet that you have made produces a changing magnetic field.
What that changing magnetic field does is to induced an emf in the aluminium ashtray due to the fact that the magnetic flux through the ashtray is changing.
This is Faraday's law in action.
The emf produces an induced current in the ashtray as it is a conductor.
That induced current flows in such a direction to produce a magnetic field in opposition t he changing magnetic field producing it.
This is Lenz's law in action.
In the case of your experiment the aluminium will try and go to a region where the change in magnetic field ie smaller ie move upwards.
This will usually mean that the ashtray will move up and across and "fall" off the electromagnet.  
Your careful arrangement of the magnetic field has meant that the ashtray is in a position of stable equilibrium so that as the tray moves up and across horizontal forces due to the interaction of the magnetic field due to the electromagnet and the induced current push the tray back.  
You may have noticed that the tray gets warmed due to the induced currents produce ohmic heating in the ashtray.  
The repulsion occurs because the aluminium is a conductor and such an effect would not be seen with an object made of an insulator like plastic.
Here is another version of your experiment where the heating effect is demonstrated.
