What is Superconductors: Definition and 146 Discussions

Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic flux fields are expelled from the material. Any material exhibiting these properties is a superconductor. Unlike an ordinary metallic conductor, whose resistance decreases gradually as its temperature is lowered even down to near absolute zero, a superconductor has a characteristic critical temperature below which the resistance drops abruptly to zero. An electric current through a loop of superconducting wire can persist indefinitely with no power source.The superconductivity phenomenon was discovered in 1911 by Dutch physicist Heike Kamerlingh Onnes. Like ferromagnetism and atomic spectral lines, superconductivity is a phenomenon which can only be explained by quantum mechanics. It is characterized by the Meissner effect, the complete ejection of magnetic field lines from the interior of the superconductor during its transitions into the superconducting state. The occurrence of the Meissner effect indicates that superconductivity cannot be understood simply as the idealization of perfect conductivity in classical physics.
In 1986, it was discovered that some cuprate-perovskite ceramic materials have a critical temperature above 90 K (−183 °C). Such a high transition temperature is theoretically impossible for a conventional superconductor, leading the materials to be termed high-temperature superconductors. The cheaply available coolant liquid nitrogen boils at 77 K, and thus the existence of superconductivity at higher temperatures than this facilitates many experiments and applications that are less practical at lower temperatures.

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  1. M

    Speed of free electrons in vacuum, plasma and superconductors?

    What is the speed of free electrons in vacuum, plasma and superconductors? Can we 'slow down' free electrons? Just how slow can we make electrons go?
  2. C

    Applying Ising Model to High Temp Superconductors

    I am curious to know the Ising model can be applied to high temperature superconducting materials. If so are there any papers significant papers on this subject that I should know about. Thanks to anyone in advance who can answer this question.
  3. T

    Effects gravity have on Superconductors

    The electron pairs, acting as bosons, all fall to the lowest energy state, and can't get enough energy (under normal operating conditions), to make the quantum jump to the next energy level, hence as they move through the conductor they don't lose energy. That is, in a nutshell, my assumptions...
  4. M

    Can anyone tell me how impurity in superconductors changes the Tc?

    I've search plenty of papers,but I still got no idea about this.Can anyone give me some clues? Thanks in advance.
  5. P

    Superconductors and Energy Conservation

    A classic problem in freshman electrodynamics is as follows: We have a capacitor (capacitance C1) charged up w/ charge Q, which means the energy in the system is: U_1 = \frac{Q^2}{2C_1}. We then disconnect the battery, and connect a second capacitor (capacitance C2) in parallel w/ the...
  6. Mentallic

    Unconventional Superconductors: Explaining Beyond BCS Theory

    I'm unsure where this is meant to go precisely, so if needed, move this thread where necessary. Our class just touched up just slightly on BCS theory. We were told that conventional superconductors (SC) with Tc<30K were explainable by this theory, while unconventional SC's with Tc>30K...
  7. M

    Understanding Superconducting Energy Storage: Principles and Applications

    Hi all! It's my first post. :cool: How is electrical energy sent into a superconducting loop for storage and taken out for use? Is there power loss during these actions? Peace!
  8. M

    Calculating Electromagnets for 4T Output without Superconductors

    anyone have equations for bitter magnets? or do i use the ones for solenoids? i need an electromagnet capable of 4T. that doesn't use super conductors >_> i have access to liquid nitrogen though.
  9. R

    Superconductors and high voltage

    I have an idea to build a electromagnet out of superconducting wire out of the Tl2Ba4Ca2Cu10Ox superconductor discovered earlier this year that's superconducting at 40 degrees below zero in Fahrenheit and I'm wanting to supply 1 million volts or a little more to it and see what happens. and...
  10. J

    Looking for comparison of superconductors

    Hi All I'm looking for a table of Tcs and normal state resistivities for a selection of 'typical' superconductors. I'm sure such a thing must exist in literature, but I'm having trouble locating it. Specifically, I've just finished a dissertation project developing a measurement technique...
  11. S

    Gravity Waves and Superconductors (Raymond Chiao)

    Berkeley's Raymond Chiao has some interesting conjecture on gravity waves: http://www.technologyreview.com/blog/arxiv/23198/ According to him, it should be possible for a superconductor to reflect gravity waves like a mirror. This then leads to all sorts of interesting possibilities...
  12. F

    Magnetic fields and superconductors

    1. I have read that external magnetic fields cannot penetrate a superconductor. Why is this? 2. Does the magnetic field produced by the superconducting current extend outside of the superconductor? And if so, what happens when the magnetic field starts to collapse, can it renter the...
  13. T

    Amplified frame-dragging effects due to superconductors?

    Hi there, This is my first post and I am guessing I should post my question here at the astrophysics section so I'm doing so (admin, if you think the topic should belong somewhere else, please move it). My question is with regards to the continued research conducted by Tajmar et al...
  14. H

    Difference between Perfect Diamagnetism and Superconductors

    Could someone please explain the difference between Perfect Diamagnetism and Superconductors in terms of the Meissner Effect and the magnetic field passing through an element of the sort. Under low temperatures in perfect diamagnetic materials if there is a magnetic field it remains the same...
  15. W

    High Temperature Superconductors

    Hello, frineds I have a question How is it possible to get High Temperature Supercondactor produced by laser radiation? Maybe we can irradiate a target and the producing plasma will serrle down substrate Do you have an idea?
  16. W

    Spontaneous Breaking Local Gauge Symmetry: Hamiltonian Formalism?

    Is it possible to describe spontaneous breaking of the local gauge symmetry in the standard Hamiltonian formalism, without any manual redefinition of the gauge field( A(r) -> A(r)+▽Λ(r) )? Detailed description of my question is given below.(Quite lengthy.. sorry.) 1. By the 'standard...
  17. I

    Uses of type I superconductors

    Does anyone know of any practical uses for a type I superconductor, where it isn't possible to use a type II (which typically have higher critical temperatures so need less cooling etc)?
  18. Redbelly98

    Exploring Superconductors: Understanding Induced EMF in Magnetic Flux Changes

    After following the thread "ideal conductor vs superconductor" a while, I am wondering about something that must have a simple answer. If you change the magnetic flux through a superconducting ring, what happens to induced emf?
  19. T

    Lorentz force in superconductors

    Hi, everyone. In a course on superconducting materials, my lecturer has suggested that in a Type I(one) superconductor, any normalconducting region containing trapped magnetic flux will feel a Lorentz force per unit volume F_L = J \times B, where J is the transport current density (vector!)...
  20. Phrak

    Characteristics of Superconductors

    What are the permeability and permissivity of type I superconductors?
  21. G

    Why do superconductors superconduct current?

    Hello, which theory or formalism is used to show the superconductors have zero resistance? I'd like to see some derivation from microscopic principles. For resistivity scattering is crucial so a static wavefunction doesn't offer an explanation? I read some basic BCS theory and have...
  22. S

    The Role of Phonons in High Temperature Superconductivity

    I'm trying to understand a bit more about high temperature superconductors. I'm familiar with BCS theory and a little bit about high temp superconductors, but I'm still confused about a bunch of stuff Why exactly is copper oxide used in high temperature superconductors? Why is this specific...
  23. T

    Fermi function for Superconductors?

    I don't really understand why the Fermi-Function is often used to describe superconductors. According to the BCS theory Cooper pairs should be Bosons with Spin 0. Wouldn't it make more sense to use the Bose-Einstein-Function? Thanks Tanja
  24. Z

    Quantized flux in superconductors

    I read that most type-2 superconductors have one quantum of flux (2*pi*h-bar/e) per flux filament (fluxon), but that a few have a different value (were fullerenes one of them?). I mentioned this to an professor I am doing some research for, and he challenged what I read. Now, I can't find what...
  25. A

    Superconductors and Gravitomagnetism

    How/why does a superconductor amplify the effects of gravitomagnetism? It must have something to do with a coherent movement of subatomic particles, right?
  26. T

    Lab report for superconductors

    Hi, I am doing a lab report for superconductors, and yeah, we have to bake them in a furnace and test their properties and all that. I am trying to find a nice book, something like an all in one jumble where it talks about the history, the theoretical properties (such as the Meissner effect)...
  27. M

    Electric resistance and superconductors

    I was reading there that if you apply an electromotive force of 1 vole to a wire with a resistance of 1 ohm it will cause a current of 1 ampere to flow. If I was to obtain a wire with no resistance at all and applied 1 volt to it would it still cause a current of 1 amp to flow or would the...
  28. wolram

    Can dark energy be explained by superconductors?

    http://arxiv.org/PS_cache/arxiv/pdf/0704/0704.2499v1.pdf This seems interesting, has anyone an idea about this research ?
  29. A

    On superconductors and magnets

    source:British physics olymp. 1995:cool: a small slab of material is placed on a dish containing liquid nitrogen.The material is a superconductor at the temperature of liquid nitrogen.A small but strong magnet is moved near and placed over the slab.The magnet is seen to wobble but remains...
  30. L

    Determining Tc value of various superconductors

    I am plotting resistance vs. thermocouple voltage (which is to be used to determine the temperature from a conversion chart) for two superconductors. I need to determine where to take the Tc value. This is difficult to determine since the "knee" is not well defined. Also, how should I guess...
  31. ZapperZ

    High Tc superconductors turn 20

    This past Sept. marked the 20th anniversary of the discovery of High-Tc superconductors. It was a discovery that turns physics, and especially condensed matter physics, upside down. A subject area that was thought to be 'dead' and fully matured, where we thought we knew everything that we were...
  32. O

    Superconductors usable as propulsion devices?

    If I were able to get a particle with mass to tunnel through a superconductor (for the sake of having a point, a long, thin, cylindrical one), would that mass's travel through the superconductor have the same equal-but-opposite-reaction effect as the same mass if it were accelerated to such...
  33. V

    Room Temperature Superconductors

    How far are we from Room Temp SCs? Have they been invented yet? I hear you can use dynamite and that get's you close to room temperature.
  34. N

    Theoretical investigation into High Tc Superconductors

    This attachement was my dissertation, my final project for my BSc in physics, just would like a proffessional opinion. Best wishes newo
  35. ZapperZ

    Magnetic neutron scattering in hole doped cuprate superconductors

    There is a good review article on inelastic neutron scattering experiments and results on hole-doped cuprate superconductors. One of the authors (Tranquada) was the first person to report experimentally on the possible existence of the stripe phase in such a compound using the same technique...
  36. N

    20 Years of High Temp Superconductors

    So we've had 20 years of high temperature superconductors and I cannot help but ask myself why isn't my power cord made out it? In all this time you would expect some kind of applications to be coming through (excepting the odd industrial application). I assume the main prolem is with the...
  37. G

    Liquid nitrogen temperature superconductors

    Hi, I have started Plysics 20 by correspondence and I can't find the answer to this question: The reason that liquid nitrogen temperature superconductors are important is that liquid nitrogen costs less than liquid helium. New technologies to store liquid helium have been developed in the...
  38. G

    O utopia: superconductors for transmission lines globally?

    o:) utopia: superconductors for transmission lines globally? o:) undefinedundefined i want to develop a model ,entailing all the parameters required to transmitt power using SUPERCONDUCTORS . IF ANYBODY CAN HELP ME PLEEZE POST THE NUMERICAL DATA REGD THE SAME ,this will be highly acknowledged...
  39. A

    Exploring the Slow Adoption of HT Superconductors: Advantages and Challenges

    Given that HTSC cables have been commercially available for some time now why has the uptake of this technology been so slow. Even allowing for the extra cost I'd have thought the advantages such as 140x the current carrying capacity, far higher efficiency etc. would outway any possible...
  40. B

    High-temperature superconductors

    Okay - I understand the idea of why superconductors work (i hope i do - it was a while ago I learned it) - namely by two electrons of 1/2 integer spin obeying Fermi-Dirac statistics, forming a pair of electrons than can behave in some circumstances like a single particle with integer spin. This...
  41. M

    Can You Create Your Own Superconductor at Home with Basic Chemistry Knowledge?

    Is it possibly to make a superconductor at home ? I mean with limited funds and ... you know. Maybe this idea is a bit crazy but I'd like to know. :biggrin:
  42. J

    Exploring the Isotope Effect in Superconductors

    I am doing a report on superconductors. One of the ideas to support the idea of bandgaps in the superconductor is the isotope effect. Unfortentualy I have been an able to find any information on how exactly the isotope effect works. Any information would be greatly appreciated, thank you...
  43. J

    Superconductors can allow a current to flow indefinately

    Superconductors can allow a current to flow indefinately. Assuming that someday room temperature superconductors are avilable, would it be possible to use them as some sort of RAM hybrid for a computer? Could information be stored indefinately, almost like using a harddrive, but much faster...
  44. D

    Questions about Superconductors | Greetings

    Greetings ! I'd like to ask a couple of Qs about superconductors: - Would a superconducting wire be affected by the lorentz force just like a normal current carrying wire or would the Meissner effect somehow prevent this due to the surface currents or something ? - What's the general...
  45. Mk

    Type II superconductors definition?

    What is the definiton of a high temperature superconductor otherwise known as Type II superconductors?
  46. jimmy p

    Why superconductors repel magnets no matter what polarity

    Hey everyone, got a quickie for u. I'm not sure if there is a proper answer for this question, but could ppl give me brief theories to why superconductors repel magnets no matter what polarity they are. thanks for any input!
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