We were taught this stuff in school, although I didn't think of that application then :-) I mean that current running through a coil induces a magnetic field.

We were taught this stuff in school, although I didn't think of that application then :-) I mean that current running through a coil induces a magnetic field. Maybe just start with a physics school book? Edit: in fact current running through a wire induces a magnetic field (actually, just electrons moving, with or without a wire), I guess the coil just gives it direction and kind of amplifies it (it's been a while).