What is Superconductor: Definition and 149 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.

View More On Wikipedia.org
Recent contents Top users
  1. T

    Does Impedance Exist in Superconductors Below Their Critical Temperature?

    Okay, I know in standard inductors the coil itself causes electrical resistance when AC current is passed through it, but I was wondering if a superconductive coil below its Tc has the same effect? Is there any impedance because the meisser effect does not allow outside magnetic fields to...
  2. C

    Light hitting a superconductor?

    can x-rays go through a superconductor when it cooled down to its superconducting state.
  3. M

    Superconductors: How to Initiate and Maintain a Current | Explained

    Hello: I have been reading up on superconductors and everywhere it mentions that once a current is set up in a superconductor, it persists. I understand this, but no where can I find any information on how in practice a current could initially be "started" in a super conductor and made to...
  4. D

    How the currernt in a superconductor is limited?

    How the currernt in a superconductor is limited?
  5. P

    EM response function of the Phase Action of a BCS superconductor

    EM response function of the "Phase Action" of a BCS superconductor Hello, I am looking for a paper in which people calculated the EM response of phase action of A BCS SC. In the book "Condensed Matter Field Theory" by Altland and Simons, on page 393 they mention such a thing in the discussion...
  6. J

    What are the dangers of slow current removal from superconducting magnets?

    If you took an insulated fully charged superconducting capacitor, and suddenly warmed it above the critical temperature, what would you observe happen? For example, if the superconductor discharged in space. What form would the energy released take?
  7. D

    Magnetic dipole above a superconductor.

    Homework Statement Consider a magnet floating over a large piece of superconductor. Treat the magnet as a perfect dipole m floating a distance h from the surface of the superconductor, which we take to be the x–y plane. The dipole is oriented at an angle of θ to the z-axis, and without loss...
  8. M

    $500 Superconductor research project?

    Hello my university is giving out little "mini" grants for undergrad research and I was wanting to get involved because it sounds fun/looks good on a resume. The winners would get $500 to spend on a research project of their choosing. All I have to do to enter is fill out some paperwork stating...
  9. Q

    Critical field for a type I superconductor

    Homework Statement Consider a type I superconducting material with a parabolic coexistence curve separating the uniform superconducting and normal phases. H is the external magnetic field and T is temperature. Ignore the tiny magnetization of the normal phase. The critical field is Hc = H0...
  10. B

    Is there a limit to the amount of energy stored in a superconductor?

    I'm curious, neglecting all the worries about temperature, etc (assume those conditions can be met)... Is there a limit to the amount of energy that can be stored in a superconductor? Is there a formula to calculate it? What causes this limit, etc? Is there a massive field generated by the...
  11. B

    Causes a superconductor to lose energy after a finite period of time

    Hi Please explain Flux Motion Resistance in Superconductors which causes a superconductor to lose energy after a finite period of time. (Theoretically it shouldn't)
  12. C

    Magnetic Track + Superconductor = Rideable Hover-Board?

    hi, A teacher at school was demonstrating some of the properties of superconductors and that got me thinking if it would be possible to get a person to hover. I did a bit of research and it seems that not only is this possible but it's already been done. I saw some videos of small toy...
  13. G

    Does a Superconducting Disc Spin When Exposed to a Spinning Magnet?

    Problem Statement In a recent exam, I was asked the following question: "A superconducting disc is suspended on strings (horizontally, flat side facing ground) and cooled below it's critical temperature. A bar magnet is placed on a spinning axle under the disc. What happens to the disc once the...
  14. R

    Varying cross section superconductor

    Here's the question: How can we describe a sudden change in the cross sectional area of a super conductor carying a current i from bigger A1 to smaller A2, such that the current density J after change is higher than Jc ? I have one scenario in my mind, the tempreture rises in the...
  15. T

    Benefits of using a superconductor to create a magnetic field at 77K

    Hello all, I'm in the process of designing my own electromagnets, and would like to know the benefits(if any) of using superconducting wire at 77K( liquid nitrogen cooled) rather than an equivalent length of copper wire cooled to those temperatures in creating a solenoid. Because the critical...
  16. G

    Supercurrent can flow forever in a superconductor

    it has always mystified me how a supercurrent can flow forever in a superconductor. seems like perpetual motion to me. it ocurrs to me now that the simplest explanation is that there is no actual current at all. that nothing is actually flowing in any supercurrent. that the supercurrent merely...
  17. V

    Critical temperature of a superconductor

    I have this problem here that I don't understand: The critical temperature of a superconductor, TC varies with the isotopic mass of the element making up the superconductor, M, according to the relation TC *square root(M) = a constant. In lead, TC = 7.184 K for the isotopic molar mass 207.7 g...
  18. B

    Liquid Superconductors: Experiments and Possibilities

    As described here: http://www3.interscience.wiley.com/journal/112748702/abstract All superconductors are solids in their superconducting state, this state of matter presently having only been observed well below the melting temperature of the solid. The discovery of high-temperature...
  19. N

    Charges passing through a superconductor

    Hi I just wanted to know if a charge passing through a superconductor will diminish its current. I know superconductors will keep a current as long as they are kept cool, and I know that a moving charge will produce a magnetic field. However, will this produced magnetic field reduce the...
  20. P

    Where Can I Purchase a Superconductor?

    I need to buy a superconductor for a simple project. I'm only demonstrating how it floats on a magnetic track. Where could I find a superconductor that will work under Liquid Nitrogen's temperature, and is around 2-5 inches in diameter? I've only been able to find very tiny (about...
  21. F

    If you add salt to liquid nitrogen,would it turn into a superconductor?

    I was wondering also if you put a magnet above it, then lifted the magnet up,would the nitrogen and salt come up too?
  22. W

    Superconductor levitating above a magnetic track?

    I have a science fair coming up for school, and while I have been doing a ton of research, I have a few questions. I am attempting to recreate an experiment in which a supercondcutor levitates back and forth along a track of permanent magnets. The track consists of 23 magnets, 3 magnets to a...
  23. Redbelly98

    New Superconductor Developed at Brookhaven Lab

    A new superconductor has been developed at Brookhaven National Laboratory: http://news.yahoo.com/s/nm/20081008/sc_nm/us_superconductor_2 The superconductor is at the junction between two non-superconducting materials, is about 1 nm thick, and has a transition temperature of 50K.
  24. MathematicalPhysicist

    Superconductor in a magnetic field.

    Problem Statement: when a superconductor of the first order is under the influence of an external magnetic field, the field is repelled from the the supercondutin material until the field reaches a critical value called the critical field H_c(T). for H>H_c the material turns into regualr metal...
  25. D

    Speed of light in a superconductor

    Could you please spot where is the fault in this reasoning? I suspect that some of the relations may not be applicable and needs to be substituted with something else (or I'm just making a gross mistake as usual...): Speed of light in a material: c=\sqrt{\frac{1}{\epsilon\mu}} where...
  26. R

    Enhancing Superconductivity with Linear Superconductors

    For a super conductor there is a maximum current after which the energy of electrons will be higher than Fermi energy and no cooper pairs will exist . Can this be evaded if we used linear superconductors rather than coils ?? thus, the motion of electron pairs could be inertial , And the...
  27. R

    Ideal conductor vs superconductor

    What is the difference, apart from the Meissner effect? What are the practical consequences of Meissner effect? How can I, by experiment, deduce whether a material is an ideal conductor or superconductor? superconductor has zero resistivity. So what happens when we apply a potential...
  28. R

    Superconductor with no current?

    Hello everyone! My brother is having a science fair coming up. He is doing it over superconductors. We have the Meissner effect down just fine, but I have this idea to pass a current through the ceramic in its superconducting state. We want to show the difference in brightness of a little...
  29. C

    Where can i purchase a superconductor?

    I have to complete a project in a weeks time but i am missing a vital part to the project. I am building a model of a levitating train and have all the magnets and tracks ready i also have liquid nitrogen ordered, unfortunately i am unable to find any form of superconductor. Any help is...
  30. N

    Meissner effect and superconductor

    Hi From what I understand the Meissner effect occurs when a current is induced in a superconductor, from a magnet, giving rise to a magnetic field from the superconductor that opposes the magnet. What stops the magnet from being completely repelled away from the superconductor when it is...
  31. B

    Solving for M in a Type 1 Superconductor Sphere

    Homework Statement Consider a sphere of type 1 superconductor with critical field Hc. (a) Show that in the Meissner regime the effective magnetisation M ithin the sphere is given by -3B_a/2\mu_0 (where Ba is the uniform applied magnetic field). (b) Show that the magnetic field at the surface...
  32. P

    Critical field for a superconductor - why?

    Cool a cylinder made from a Type I superconducting material below the superconducting transition temperature. Apply a magnetic field parallel to the cylinder. The cylinder expels the flux.. up until the field reaches a critical value. Why does a critical value exist? That is, why doesn't...
  33. W

    Superconductor 'meissner effect' help

    Hi, does anyone know how superconductors will oppose a magnetic flux even if it is unchanging. Thanks
  34. ZapperZ

    Silicon becomes a superconductor

    If you missed the paper in this week's Nature, let's just say that this is an unexpected discovery. You can read a report of it in PhysicsWeb http://physicsweb.org/articles/news/10/11/19/1 Zz.
  35. Z

    Ceramic can become a superconductor

    "ceramic" can become a superconductor State why some insulatores such "ceramic " can become a superconductor when cooled to a temprature of 0 K. :confused:
  36. S

    Question about Superconductor Flux Pinning

    As I understand it, flux pinning is when a material becomes a superconductor in the presence of a magnetic field, say from a permanent magnet, and the lines of flux from the permanent magnet are trapped inside the superconductor causing the superconductor to be held ("pinned") at a fixed...
  37. A

    High Temperature Superconductor Motors - Availability, Efficiency & More

    please help me in cllecting information about High Temperature Superconductor motor. Are they available in the market? how effecient are they? I need to know all their details, properties, design, advanteges. Thanks all
  38. C

    Trying to fabricate a 1-2-3 YBCO superconductor

    Hey everybody, just wanted to know if anyone had any experience with superconductor fabrication? I know the whole crystal lattice structure thing is more chemistry than physics but I figured I could post in both places. Anyways, I am currenty trying to fabricate a 1-2-3 YBCO superconductor...
  39. M

    Is There a Way to Prove Normalization of the BCS Equation?

    hi i have superconductor question, need someone familiar with this field. does anyone know how to prove normalization of bcs equation? <psi|psi>=1 given uk^2 + vk^2 =1 i went through the Heisenberg algebra but still can't solve it. any guide?
  40. S

    Can Magnetism Alter Quantum Phase in Superconductors?

    in deriving quantization of flux in superconductor ring, the momentum of cooper pair p: p=\hbar\nabla\theta=e^*(\Lambda J_s + A) then integrate around the ring, \hbar\oint\nabla\theta dl=e^*\oint(\Lambda J_s + A)dl using stoke's theorem and integrate sufficiently deep in the ring where...
  41. S

    MgB2 Brittle? Superconductor q's & Experiments

    1. is MgB2 brittle? can we draw it like wire and wind it up make a coil/electromagnet with it? 2. liquid nitrogen boils at 77K and freezes at 63K. most superconductor experiments use liquid nitrogen, so does it mean most applications use this temperature range (eg. for squid)? what about...
  42. L

    Levitating magnet and rotating superconductor,

    Look at this figure. http://img223.imageshack.us/img223/2136/rotatingsuperconductorandmagne.th.png What will happen to the repulsive force between magnet and superconductor?Would the repulsive force increase with rotation?
  43. S

    What Technologies are Used to Measure Near 0 K Temperatures?

    1. why, instead of cooper pair, don't we have a group of N electrons coupled for superconductivity? 2. Has cooper pair been observed experimentally? 3. What kind of thermometer do we used to measure near 0 K temperature? 4. Has Josephson tuneling for oxyde high Tc been made? Because...
  44. S

    Simple superconductor question

    suppose we have a superconductor speciment above Tc, and we put it in magnetic field. then we cool it down to below Tc, then a screening current is produced. where does the electron get the energy to initiate the current on the first time?
  45. Crumbles

    All this superconductor business

    I am new to superconductors and how they work. :confused: Could anybody maybe explain how currents actually arise in a superconductor? Is it just by placing the superconductor in a B-field that causes a current due to the expulsion of the external field (Messiner Effect)? If so, is that...
  46. D

    Superconductors and Conductors: Connections and Possibilities

    Greetings ! I was wondering how (or if) a superconducor can be connected to a "normal" conductor in an electric circuit ? I guess the conductor-superconductor connection is easy, but how do you avoid problems at the reverse connection - do you need some amplifier or something. Also...
  47. C

    Exploring the Wonders of Superconductors

    Ok, I can't exactly run out to the store and put some of these in my freezer to experiment with (hurry up guys :smile:), so here's just some questions I was thinking about. - Superconductors would have very near zero resistance (part of their definition) so would that mean that the current...
  48. S

    Why is a superconductor a diamagnet?

    Why is a superconductor a diamagnet?
  49. Ivan Seeking

    Impulse Gravity Generator Based on Charged YBa_2Cu_3O_{7-y} Superconductor

    Assuming that this must be controversial at best, I am posting FYI. Impulse Gravity Generator Based on Charged YBa_2Cu_3O_{7-y} Superconductor with Composite Crystal Structure http://xxx.lanl.gov/abs/physics/0108005
Back
Top