A quick question. Let's say you had an infinitely long wire carrying a constant current, and a straight piece of wire parallel to it a certain distance away. Obviously, the current, being a motion of charges, will generate a magnetic field, with its curl being equal to the electrical permittivity times the charge density. As well, this magnetic field will induce an electromotive force in the piece of wire. However, the question I have is this: it's obvious to me that there is an electric potential produced by the current-carrying wire on the piece of wire, but is there a potential DIFFERENCE? I'm fairly sure that the induced electric field won't have a curl--the magnetic field is basically constant--but I'm not sure about the mere presence of an electric field at all.