|MadSci Network: Physics|
It seems you are really talking about two different things soÖ First: Letís clear up, I hope, a little confusion. Moving any charged particles will produce a magnetic field around them. If we move these particles across an external magnetic field the two fields interact and the particles feel a force mutually perpendicular to the external field and their direction of motion. This is the force that we say induces a current or voltage and it has nothing to do with whether or not the particles in question (electrons in the case of wires) each have an inherent individual magnetic field of their own or not. Most high school and freshman college physics textbooks will have some pretty good pictures of this behavior. At the atomic level in a material like copper there is about one electron per atom that is essentially free to move about in the wire. If this wire is moved across an outside magnetic field then these electrons are seen as charges moving across that field and are pushed in one direction or the other by the interaction described above. What reverses direction is the force acting on them not their own individual magnetic fields. Since copper is a conductor in which the electrons are free to move then they will try to do so resulting in an induced current or voltage along the direction in which they are forced by the external field. Second: Not all charged particles have inherent magnetic fields but it is true that electrons do. So do protons for that matter. You can imagine them as tiny bar magnets (dipoles). When you read about flipping, reversing, or aligning these fields you are most likely discussing either the formation of magnetic domains as in ferromagnetism, (here again the physics text will come in handy with some good pictures) or some kind of magnetic resonance process, Electron Spin Resonance (ESR), Nuclear Magnetic Resonance (NMR), or Magnetic Resonance Imaging (MRI). These last three and their relatives involve trying to line up some of the individual electron, (or proton), fields with an external field and then trying to flip them over with an outside input of electromagnetic energy (usually radio or microwave). Exactly which frequencies are required tell us about the atoms with which these electrons interact so you are right in the sense that the net field of the atom is important too. At ordinary temperatures and typical field strengths random thermal motion will keep the majority of these particles jumbled with respect to the external field so we donít notice this affecting what we discussed in the first part of this answer. With a strong enough field however and sensitive enough detectors we can measure the effect for the second case and it turns out to be a very important tool for science and medicine.
Try the links in the MadSci Library for more information on Physics.