Содержание
- 2. The fascinating phenomenon of superconductivity and its potential applications have attracted the attention of scientists, engineers
- 3. A few years earlier he had become the first person to liquefy helium, which has a
- 4. Intense research has taken place to discover new superconductors, to understand the physics that underlies the
- 5. Graph showing the resistance of a specimen of mercury versus absolute temperature.
- 6. The Periodic Table showing all known elemental superconductors and their critical temperatures.
- 7. Since this initial discovery, many more elements have been discovered to be superconductors. The dark pink
- 8. It is worth noting that copper ( Cu, Z = 29 ), silver ( Ag, Z
- 9. At sufficiently low temperature, two oppositely spinning and oppositely travelling electrons can attract each other indirectly
- 10. The electron 1 distorts the lattice around it and changes its vibration as it passes through
- 11. A consequence of this interaction is that pairs of electrons are coupled together, and all of
- 12. It takes a significant amount of energy to scatter an electron from the condensate – more
- 13. By the early 1960s there had been major advances in superconductor technology, with the discovery of
- 14. He predicted that a current could flow between two superconductors that were separated by a very
- 15. The critical temperature Tc of various superconductors plotted against their discovery date.
- 16. Properties of superconductors a) Zero electrical resistance - The most obvious characteristic of a superconductor is
- 17. c) The Meissner effect - when a magnetic field is applied to a sample of tin,
- 18. A comparison of the response of a perfect conductor, (a) and (b), and a superconductor, (c)
- 19. Comparison between perfect conductor (zero resistance) and superconductor. 1) part a) and b) of the figure
- 20. In contrast, part (b) shows that cooling a perfect conductor to below its critical temperature in
- 21. 2) part c) and d) (superconductor) Whether a material is cooled below its superconducting critical temperature
- 22. d) Perfect diamagnetism Diamagnetism is due to currents induced in atomic orbitals by an applied magnetic
- 23. e) Critical magnetic field An important characteristic of a superconductor is that its normal resistance is
- 24. Experiments indicate that the critical magnetic field strength depends on temperature, and the form of this
- 25. The temperature dependences of the critical magnetic field strengths of some materials
- 26. The critical temperatures Tc and critical magnetic field strengths Bc(0) for various superconducting elements.
- 27. f) Critical current The current density for a steady current flowing along a wire in its
- 28. The London equations ( local model) A simple but useful description of the electrodynamics of superconductivity
- 29. . London brothers proposed the following equation which relates current and magnetic field in a superconductor.
- 30. Penetration depth The characteristic length, λ, associated with the decay of the magnetic field at the
- 31. The penetration of a magnetic field into a superconducting material, showing the penetration depth.
- 32. The number density of superconducting electrons depends on temperature, so the penetration depth is temperature dependent.
- 33. The penetration depth λ as a function of temperature for tin.
- 34. Classifications of superconductors. Based on their behaviour in an applied field, superconductors are classified into two
- 35. For simplicity, let us consider a long cylindrical specimen of type-II material, and apply a field
- 36. Below a certain critical field strength, known as the lower critical field strength and denoted by
- 37. Eventually, a second critical field strength, the upper critical field strength B c2, is reached, above
- 38. Temperature dependence of the lower critical field strength (Bc1) and upper critical field strength ( B
- 39. The normal cores that exist in type-II superconductors in the mixed state are not sharply delineated.
- 40. Number density of super electrons n s and magnetic field strength B around normal cores in
- 41. You can see from the figure that the coherence length ξ, the characteristic distance for changes
- 42. Critical currents in type-II superconductors The high values of the upper critical field strength Bc2 of
- 43. This problem is related to the interaction between the current flowing through a type-II superconductor in
- 44. This Lorentz force can cause the cores and their associated magnetic flux to move, and the
- 45. This is done by introducing defects into the crystalline structure, particularly by preparing the material in
- 46. Application areas of superconductors In Medical areas - magnetic resonance imaging - biotechnical engineering. In Electronics
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