Superconductivity introduction and superconductivity history, Physics

INTRODUCTION: Superconductivity is a phenomenon takes place in certain materials at low temperatures. Characterized by precisely zero electrical resistance. Superconductors have two exceptional features.

HISTORY: Superconductors, materials that have no resistance to the flow of electricity, are one of the last great frontiers of scientific discovery. The theories that explain superconductor behaviour seem to be constantly under review. In 1911 superconductivity was first observed in mercury by Dutch physicist Heike kamerlingh acnes of Leiden University. When he cooled it to the temperature of liquid helium, 4 degrees Kelvin (-4520F, -2690C), its resistance suddenly disappeared. The Kelvin scale shows an “absolute” scale of temperature. Thus, it was necessary for acnes to come within 4 degrees of the coldest temperature that is theoretically attainable to witness the phenomenon of superconductivity later, in 1913; he won a Nobel in physics for his research in this area. The next huge milestone in understanding how matters perform at extreme cold temperatures occurred in 1933. German researchers Walter Meissner and Robber Ochsenfeld discovered that a superconducting material will repel a magnetic field (below graphic). A magnet moving by a conductor induces currents in the conductor. This is the principal on which the electric generator works. But, in a superconductor the induced currents precisely mirror the field that would have otherwise pierced the superconducting material causing the magnet to be repulsed. This phenomenon known as strong diamagnetism and is today often referred to as the “Meissner effect” (an eponym). The Meissner effect is so powerful that a magnet can really be levitated over a superconductive material. In succeeding decades other superconducting metals, alloys and compounds were revealed. In 1941 niobium nitride was originate to superconducting at 16K. In 1953 vanadium silicon showed superconductive properties at 17.5k. And, in 1962 scientist at wasting house developed the first commercial superconductive wire, an alloy of niobium and titanium. High energy particle accelerator electromagnets made of copper clad niobium titanium were than developed in the 1960s at the Ruther food Appleton laboratory in the U.K. And were first employed in the superconducting accelerator at the Fermi lab Everton in the U.S in 1987. The first widely accepted theoretical understanding of superconductivity was advanced in 1957 by American physicists John Bardeen, Leon Copper, and John Schrieffer. Their theories of superconductivity became known as the BCS theory derived by the first letter of each man’s last name and won them a Nobel Prize in 1972. The mathematically complex BCS theory explained superconductivity at temperature loses to absolute zero for elements and simple alloys. Another significant theoretical advancement came in 1962 when Bream D. Josephson predicated that electrical current would flow between two electrical current would flow between two superconducting materials even when they are separated by a non superconductor or insulator. This tunnelling phenomenon is today known as the “Josephson effect” and has been applied to electronic devices such as the SQUID (AN instrument capable of detecting even the weakest magnetic fields). It has been started that the resistivity of most metals increases with increases in temperature and vice-versa. There are some metals and chemical compounds whose resistivity become zero when their temperature is brought at 00K (-2730C). At this stage such metals or compounds are said to have attained super conductivity. The two distinctly different types of behaviour are dissipated. Superconductivity occurred in a wide verity of materials, including simple elements like tin and aluminium, various metallic alloys, some heavily doped semiconductors, and certain ceramic compounds containing planes of copper and the unconventional super conductor. Superconductivity does not occur in noble metals like Gold and Silver, not is ferromagnetic metals.

Posted Date: 7/9/2012 2:36:30 AM | Location : United States

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