I am revisiting a topic discussed in earlier threads, because I feel the answers given there are either incomprehensible or mistaken (or both). It is well known that the force generated by a magnetic field acting on a moving charged particle is perpendicular to the particle's motion, and that it therefore cannot "do work" on the particle. That is, it can change the particle's direction, but not its kinetic energy. The question, then, is something along the lines of "How can electromagnets pick up cars?", the implication being that the car is clearly increasing its potential energy when it moves toward the magnet. The proposed answers take several forms. Some think the question is related to conservation of energy, and point out that the energy really comes from the generator, or the power company. This misses the point. Some vanish into thickets of mathematical obscurity. Many seem to feel that the "answer" is so complicated that it is foolhardy to pursue it, or else that a detailed answer must lie in the realm of quantum mechanics or special relativity. Finally, it is frequently stated that there must be electric fields operating to lift the car, since the magnetic field cannot. The question of where exactly these electric fields come from trails off into the "too hard" response. I think a large part of the confusion arises because the discussion overlooks a crucial aspect of the situation. Specifically, if you look at the behavior of, say, a nail, being picked up by a permanent magnet, you can say that the nail moves so as to increase the flux density passing through it. Which is to say, it goes where the lines of magnetic force are closer together. Since those lines radiate outward from the poles of the magnet, any reasonably compact geometry will ensure that the nail moves towards the magnet. But this requires that the magnetic field be diverging, and therefore, that there is no direction which is "the direction of the magnetic field". If it were somehow possible to make a magnetic field which did not diverge in some region of space (as I suppose it may well be), a nail placed in the region would not move toward the magnet. Comments?