OK, I think this fits under physical chemistry. As I understand magnetism, it involves aligning the electron spin of most of the atoms in a material, such as iron. Once all the electrons are spinning the same way (I don't know much about how this works), it will have a positive and negative end. Can someone explain why in simple terms?
Now for electromagnets, as you apply more current, not voltage, to a coil of wires over a ferrous core, the strength of the magnetic field will increase. I think you get more flux lines or something like that. Problem with adding additional current, is added heat, and you're likely to melt the insulation of the wires and short out the coil to the core. What would be a better way to add more current to a coil, and why does flowing electrons produce so much heat? Has something to do with resistance, right? Cause superconducters are really good at conducting (hence the name), and produce neglible heat, which means theoretically.. I could cram a lot more power through a liquid nitrogen cooled wire?