Abstract
PROF. J. C. MCLENNAN gave the twenty-fifth Kelvin Lecture before the Institution of Electrical Engineers on April 26, taking as his subject “Electrical Phenomena at Very Low Temperatures”. In 1823 Faraday succeeded in liquefying chlorine and afterwards succeeded in liquefying many other gases, but he failed to liquefy oxygen, nitrogen and hydrogen as he was unable to obtain the requisite low temperature. At the end of the War> a large stock of helium was available in Toronto, and this gas was successfully liquefied in 1923, a century after Faraday's experiment with chlorine. By evaporating liquid helium and thus reaching an absolute temperature of 0-7° K., Keesom of Leyden successfully solidified this element in February 1932. The liquid was subjected to a pressure of 175 atmospheres and surrounded by rapidly evaporating liquid helium. The reason why liquid oxygen, hydrogen and helium are very good insulators is probably because the electrons are closely bound to the nuclei. In 1911, Kamerlingh Onnes found that the resistance of mercury vanishes suddenly at 4-2°K. and that some other metals behave similarly at definite low temperatures. Most metals show no trace of this supraconductivity even when great pains are taken to ensure their purity. Certain alloys have been found to become supraconductive. This supraconductivity can be destroyed by placing them in a magnetic field. The lower the temperature the greater the magnetising force necessary to destroy the supraconductivity. By suddenly destroying the magnetic field surrounding a ring of supraconductive metal, a current can be set up in it if its temperature be below the transition point. This current is quite independent of the nature of the metal and depends only on the intensity of the original induction. It looks as if the results of low temperature research would throw light on the nature of magnetism.
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Electrical Phenomena at Very Low Temperatures. Nature 133, 715 (1934). https://doi.org/10.1038/133715b0
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DOI: https://doi.org/10.1038/133715b0