Hi Bob, On Sat, Nov 14, 2015 at 8:51 AM, Bob Cook <[email protected]> wrote:
Eric and Dave-- > > I agree with David’s assessment. > Just to be clear, I don't disagree with Dave. His point is a good one. > In addition, since angular momentum must be conserved, the effective > circulation of electrons in a loop wants to stay that way. Magnetic fields > are much like electric fields—if established and left alone, they remain > unchanged. The charge does not “evaporate” with time nor does it move > because of the mass inertia associated with it. > Here I think you swapped the concept of "magnetic dipole moment" with that of "Coulomb attraction." The electrons can continue to have their (monopole) charge, even as the state of the superconducting magnet slowly degrades through radiation via non-resistive pathways (although I don't think this is something that would necessarily happen; but it's a question Maxwell and his contemporaries must have thought about). For this reason when I think of magnetism I think of the rotation or circulation of something. Two interesting points to note: we humans must expend a lot of energy to set up the conditions for superconductivity while nature appears to do it effortlessly. Second, those electrons in their superconducting currents must have been given a good spin of the wheel for tiny neodymium magnets to be able to accomplish this: https://en.wikipedia.org/wiki/File:Neodymium_magnet_lifting_spheres.jpg Eric
