I'm trying to make an interior rotating mangetic field that will induce electron flow in an encapsulated closed loop coil. What I'm constructing at this time (not finished yet) is a rotating (0 - 1600rpm+) neodymium permanet magnet setup in a Halbach Array assembly. I understand that inorder for the coil of wire to produce a field it must be changing, correct? A constant rotating field will not produce/induce the field desired. How can I produce changing electron flow in the coil? I suspect that once this is figured out, the coil will produce a field on the interior (between the coil and the Hallbac Array rotor) as well as the exterior of the coil assembly. The strongest "exterior" field is what I'm trying to create as well as, once the Halbach rotor has spun down to zero rpm there will be no magnetic field produced. If my description is not clear, I'll try to draw what I'm doing but I'm pc graphicly challenged. Thanks for all you help.