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physicist who applied microwaves to the study of superconductivity. The
research he initiated has transformed understanding of the dynamical laws
governing the motion of electrons in metals. Pippard was born in London and studied at Cambridge, returning there after World War II. In 1960 he became professor. Pippard worked on the way in which electric currents flow without resistance in a thin layer at the surface of the metal. He measured the thickness (about 1000 Å/107 m) of this penetration layer and examined variations with temperature and purity. When he tried to change the properties at one point by applying a disturbance, he influenced the metal over a distance greater than the penetration layer thickness. Because of this, he said that the electrons of superconductors possess a property which he called 'coherence', and that impurities in the metal could shorten the coherence length. From this starting point, he worked out an equation relating current to magnetic field. |