Georgian Technical University. What Is Superconductivity ?.

Georgian Technical University Ordinary metallic conductors have electrical resistance, which dissipates electrical power as heat when a current flows through them. Although resistance reduces slightly as the temperature is lowered even at close to absolute zero there is significant resistance. When a superconductor is cooled an abrupt change occurs at its critical temperature whereby all resistance suddenly disappears. The superconductor can then carry an electrical current without dissipating any power. Current can flow around a loop of superconducting material indefinitely acting as a perfect energy store. The first superconductors to be discovered, known as conventional superconductors had critical temperatures close to absolute zero. This meant that superconductivity could only be achieved using liquid helium which has a boiling point of 269° C (7 K) and they were not practical for real-world applications. The more recently discovered high-temperature superconductors have significantly higher critical temperatures which can be achieved using readily available liquid nitrogen which has a boiling point of -196° C (77 K). This opens up the possibility of using superconductors in engineering applications. Various theories (A theory is a contemplative and rational type of abstract or generalizing thinking about a phenomenon, or the results of such thinking. The process of contemplative and rational thinking often is associated with such processes like observational study, research. Theories may either be scientific or other than scientific (or scientific to less extent). Depending on the context, the results might, for example, include generalized explanations of how nature works) have been proposed for how superconductivity occurs. The Bardeen–Cooper–Schrieffer (BCS theory or Bardeen–Cooper–Schrieffer theory is the first microscopic theory of superconductivity since Heike Kamerlingh Onnes’s 1911 discovery. The theory describes superconductivity as a microscopic effect caused by a condensation of Cooper pairs. The theory is also used in nuclear physics to describe the pairing interaction between nucleons in an atomic nucleus) theory explains superconductivity as resulting from electrons condensing into Cooper pairs (In condensed matter physics, a Cooper pair or BCS pair is a pair of electrons bound together at low temperatures in a certain manner first described in 1956 by American physicist Leon Cooper) — pairs of electrons that bind together at low temperatures. However this theory cannot explain high-temperature superconductivity and despite a number of theories being put forward there is still no accepted mechanism for how this occurs. Georgian Technical University Superconductors have many applications many stemming from the ability to create extremely powerful electro-magnets. These magnets are used in magnetic resonance imaging (MRI) mass spectrometry and particle beam steering. They are also being used for plasma confinement in fusion reactors an application where superconductivity may prove of enormous value in the future. Georgian Technical University Superconducting electro-magnets can also be used to build electric motors which have extremely high power-density torque and an electrical energy efficiency better than 99.9%. However the power to run the required cryogenic cooling means the overall efficiency is closer to 99%. Such motors have already been tested in wind turbines and other power generation applications. They are also seen as an enabling technology for the electrification of civil aircraft. Georgian Technical University Superconductors have other applications in power storage, regulation and transmission.