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Superconductivity

Superconductivity is a property of certain materials that allows them to have zero electrical resistance below a certain temperature. Heike Kamerlingh Onnes found it on April 8, 1911.


As with ferromagnetism and atomic spectral lines, superconductivity is a quantum mechanical phenomenon.


The Meissner effect, which describes the entire ejection of magnetic field lines from the inside of a superconductor upon its transition to the superconducting state, is a defining characteristic.

The Meissner effect indicates that superconductivity cannot be seen as a classical physics idealisation of perfect conductivity. As the temperature of a metallic conductor decreases, the electrical resistivity of the conductor decreases proportionately. This drop is limited by impurities and other faults in common conductors, such as copper or silver.


Even at absolute zero, a real sample of a normal conductor exhibits resistance. When cooled below its critical temperature, a superconductor's resistance rapidly decreases to zero. An electric current travelling in a loop of superconducting wire can exist indefinitely in the absence of a power source.



According to 1986 research, certain cuprate-perovskite ceramic materials have a critical temperature greater than 90 K (-183 °C). Due to the fact that a standard superconductor is incapable of achieving such a high transition temperature, these materials are referred to as high-temperature superconductors.


Liquid nitrogen boils at 77 K, enabling a variety of experiments and uses that would be impractical at lower temperatures.




Low-Temperature Superconductors Vs High-Temperature Superconductors


Due to the fact that high-temperature superconductors are not yet affordable enough to provide the required high, stable, and massive volume fields, magnets frequently use low-temperature superconductors (LTS), despite the requirement to cool LTS equipment to liquid helium temperatures.


Until recently, high-temperature superconductors (HTS) had few practical applications. HTS superconductors conduct electricity up to the boiling point of liquid nitrogen, which makes cooling them more cost-effective than low-temperature superconductors (LTS).


The difficulty with HTS technology is that the only accessible high-temperature superconductors are brittle ceramics that are expensive to make and difficult to form into wires or other useful shapes.



Additionally, because HTS can withstand far higher magnetic fields than LTS, it is being studied for very high-field inserts into LTS magnets operating at liquid helium temperatures.




Applications of superconductivity in technology


MRI and NMR: At the moment, the primary application of superconductivity is in the generation of large-volume, stable magnetic fields for MRI (Magnetic Resonance Imaging) and NMR (Nuclear Magnetic Resonance Imaging). This is a multibillion-dollar market for companies like Oxford Instruments and Siemens.


Research Projects: Due to the fact that copper has a finite field strength, superconductors are also used in high-field research magnets.




Among the promising future industrial and commercial applications of HTS are induction heaters, transformers, fault current limiters, energy storage, motors and generators, fusion reactors, and magnetic levitation devices.


In early applications, the benefit of reduced size, weight, or the ability to switch current quickly (fault current limiters) will outweigh the additional expense. In the long run, as the cost of conductors lowers HTS systems should be competitive in a significantly broader variety of applications based on their energy efficiency alone.


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