Advances in Superconductors and their Uses

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Advances in Superconductors and their Uses A superconductor is an element or compound that will conduct electricity without resistance below a cretin temperature. The phenomenon was discovered in 1911 by Kamerlingh Onnes, who found that the resistance of mercury dropped suddenly to zero at a temperature of about 4.2°K. For the next 75 years there followed a rather steady string of announcements of new materials that become superconducting near absolute zero. A major breakthrough occurred in 1986 when Karl Alexander Müller and J. Georg Bednorz announced that they had discovered a new class of copper-oxide materials that become superconducting at temperatures exceeding 70°K. The work of Müller and Bednorz, which earned them the Nobel Prize in Physics in 1987, precipitated a host of discoveries of other high-temperature superconductors that exhibit lossless electrical flow at temperatures up to 125°K. Classical superconductivity (superconductivity at temperatures near absolute zero) is displayed by some metals, including zinc, magnesium, lead, gray tin, aluminum, mercury, and cadmium. Other metals, such as molybdenum, may exhibit superconductivity after high purification. Alloys (e.g., two parts of gold to one part of bismuth) and such compounds as tungsten carbide and lead sulfide may also be superconductors. Thin films of normal metals and superconductors that are brought into contact can form superconductive electronic devices, which replace transistors in some applications. An interesting aspect of the phenomenon is the continued flow of current in a superconducting circuit after the source of current has been shut off: for example, if a lead ring is immersed in liquid helium, an electric current that is induced magnetically ... ... middle of paper ... ...llion dollars to build a MAGLEV train at one of seven proposed sites. And Germany's commercial MAGLEV is expected to become operational in 2006. An area where superconductors can perform a life-saving function is in the field of biomagnetism. Doctors need a non-invasive means of determining what's going on inside the human body. By impinging a strong superconductor-derived magnetic field into the body, hydrogen atoms that exist in the body's water and fat molecules are forced to accept energy from the magnetic field. They then release this energy at a frequency that can be detected and displayed graphically by a computer. Magnetic Resonance Imaging (MRI) was actually discovered in the mid 1940's. But, has only recently become an indispensable medical tool with the development of powerful computers to quickly process the large volume of data that is generated.

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