SUPERCONDUCTIVITY
In case of a conductor when the temperature increases then its electrical resistance also increases because it has positive temperature coefficient of resistance. It means if we decrease the temperature then the electrical resistance of conductor will also decrease. In some materials when we go on decreasing the temperature then at a particular temperature known as critical temperature the electrical resistance of conductor becomes zero. Thus conductor becomes superconductor. This phenomenon is called superconductivity. Critical temperature for mercury is 4.2K , Lead 7.2K and Tl-Ba-Cu-oxide 125K.
It means the electrical resistance of mercury becomes zero at 4.2K temperature.
One of the truly remarkable features of superconductors is that once a current is set up in them, it persists without any applied potential difference (because R " 0). Steady currents have been observed to persist in superconducting loops for several years with no apparent decay! An important and useful application of superconductivity is in the development of superconducting magnets, in which the magnitudes of the magnetic field are about ten times greater than those produced by the best normal electromagnets. Such superconducting magnets are being considered as a means of storing energy.
Superconducting magnets are currently used in medical magnetic resonance imaging (MRI) units, which produce high-quality images of internal organs without the need for excessive exposure of patients to x-rays or other harmful radiation.
Applications
(i) Superconductors form the basis of energy saving power systems, namely the superconducting generators, which are smaller in size and weight, in comparison with conventional generators.
(ii) Superconducting magnets have been used to levitate trains above its rails. They can be driven at high speed with minimal expenditure of energy.
(iii) Superconducting magnetic propulsion systems may be used to launch satellites into orbits directly from the earth without the use of rockets.
(iv) High efficiency ore–separating machines may be built using superconducting magnets which can be used to separate tumor cells from healthy cells by high gradient magnetic separation method.
(v) Since the current in a superconducting wire can flow without any change in magnitude, it can be used for transmission lines.
(vi) Superconductors can be used as memory or storage elements in computers.
In case of a conductor when the temperature increases then its electrical resistance also increases because it has positive temperature coefficient of resistance. It means if we decrease the temperature then the electrical resistance of conductor will also decrease. In some materials when we go on decreasing the temperature then at a particular temperature known as critical temperature the electrical resistance of conductor becomes zero. Thus conductor becomes superconductor. This phenomenon is called superconductivity. Critical temperature for mercury is 4.2K , Lead 7.2K and Tl-Ba-Cu-oxide 125K.
It means the electrical resistance of mercury becomes zero at 4.2K temperature.
One of the truly remarkable features of superconductors is that once a current is set up in them, it persists without any applied potential difference (because R " 0). Steady currents have been observed to persist in superconducting loops for several years with no apparent decay! An important and useful application of superconductivity is in the development of superconducting magnets, in which the magnitudes of the magnetic field are about ten times greater than those produced by the best normal electromagnets. Such superconducting magnets are being considered as a means of storing energy.
Superconducting magnets are currently used in medical magnetic resonance imaging (MRI) units, which produce high-quality images of internal organs without the need for excessive exposure of patients to x-rays or other harmful radiation.
Applications
(i) Superconductors form the basis of energy saving power systems, namely the superconducting generators, which are smaller in size and weight, in comparison with conventional generators.
(ii) Superconducting magnets have been used to levitate trains above its rails. They can be driven at high speed with minimal expenditure of energy.
(iii) Superconducting magnetic propulsion systems may be used to launch satellites into orbits directly from the earth without the use of rockets.
(iv) High efficiency ore–separating machines may be built using superconducting magnets which can be used to separate tumor cells from healthy cells by high gradient magnetic separation method.
(v) Since the current in a superconducting wire can flow without any change in magnitude, it can be used for transmission lines.
(vi) Superconductors can be used as memory or storage elements in computers.
For detailed study visit:-
http://www.extremetech.com/extreme/208651-what-is-superconductivity
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