Abstract
IT has long been known that the electrical resistance of metals falls with a reduction of temperature in an approximately straight line law, indicating that, in the neighbourhood of absolute zero, there would be no resistance whatever. Prof. H. Kamerlingh Onnes, of Leyden, has carried experiments on this subject down to extremely low temperatures, and has found that it is at a point a few degrees above absolute zero that the resistance of certain pure metals practically vanishes. His later experiments illustrate the properties of these almost resistanceless bodies, or, as he terms them, “super-conductors,” in a very striking way. Taking a closed coil of lead wire, he cooled it down by immersion in liquid helium to a temperature at which its resistance is of the order of 2 × 10-10 that at normal temperatures. He then induced a current in the coil, which, instead of ceasing with the E.M.F., was shown to persist with scarcely sensible diminution for as long a period as the coil could be kept cold. As there was practically no resistance, there was practically no dissipation of energy, and the system behaved like the imagined molecular currents of Ampère, and realised the conception of Maxwell as to a conductor without resistance.
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Experimental Demonstration of an Ampere Molecular Current in a Nearly Perfect Conductor . Nature 93, 481 (1914). https://doi.org/10.1038/093481b0
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DOI: https://doi.org/10.1038/093481b0