- #246
Q-reeus
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And here's the part from that link that matters re Ampere model:harrylin said:I thought to use the Ampere model of permanent magnets: https://en.wikipedia.org/wiki/Force_...C3.A8re_model
[emphasis added]This is is in reference to the field generated by a fixed magnet - assuming such tiny loop currents have their currents sustained against any perturbation. It's a convenient fiction but ignores the fundamental problem of how such zero resistance loops can be assembled to form a magnet in the first place, or how if such a miracle of technology were possible, subsequent diamagnetism in respect of Lenz's law could be avoided. Intrinsic moments suffer no such problems.That is why Ampere per meter is the correct unit of magnetism, even though these small current loops are not really present in a permanent magnet.
The validity of Ampere's model means that it is allowable to think of the magnetic material as if it consists of current-loops, and the total effect is the sum of the effect of each current-loop, and so the magnetic effect of a real magnet can be computed as the sum of magnetic effects of tiny pieces of magnetic material that are at a distance
Intrinsic moments. Easy. Well, fine details are complicated, but essentially, one cannot explain permanent magnetism, especially ferromagnetism, via classical loop currents. Your magnetic force formulas are then apt - just don't yield to the pressure here to apply double accounting by supposing the purely formal E.j 'work' done on those fictitious Amperian currents is real. It aint.If you hold that a current loop is not a valid model for determining if a permanent magnet does work in classical mechanics, please replace it by a model that you do accept and redo the analysis.