recently really got myself wet in the subject of electricity and magnets. done a couple of homework and it seems that everyone utilizes magnets and batteries to project the object through the coils center to induce energy, but i'm wondering why is that? i guess the answer i'm looking for is does any regular old material work, for ex. a simple iron or steel object, being projected through the coil to induce energy, does it work that way or does it really have to be magnets/batteries? if not, is there any other possible way? i heard of electrical coating... but that's too much of a far reach.