Abstract
I WOULD like to comment, if rather tardily, on one paragraph of Prof. Ferraro's review1 of my book, Electromagnetism and Relativity 2. He says: “Prof. Cullwick appears to be under a misapprehension about the nature of the magnetic energy of a system of electric currents… we read that ‘the hypothesis is introduced that the magnetic energy of a current circuit is the same as the kinetic energy of the effective conduction electrons, by virtue of their mean velocity along the wire’. The author then derives from this hypothesis a linear relation between the magnetic vector potential and the mean velocity of the charges… the hypothesis appears to be rather misleading. It is used, in the chapter on superconductors to derive the familiar equations due to F. and H. London. Here the application is legitimate and indeed the linear relation mentioned above was first derived in connexion with the phenomenological theory of superconductors. But the relation cannot be universally true since it would seem to carry with it the implication that all conductors are superconductors”.
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References
Nature, 182, 1045 (1958).
Longmans, Green and Co. (1957); second ed. (1959).
London, F., Superfluids, 1, 66 (Wiley, New York, 1950).
(a) Maxwell, J. C., A Treatise on Electricity and Magnetism, 2, §552 (third ed., 1892); (b) ibid., §636.
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CULLWICK, E. Magnetic Energy. Nature 189, 565–566 (1961). https://doi.org/10.1038/189565a0
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DOI: https://doi.org/10.1038/189565a0
