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Super conductor/insulator question.

  1. Oct 21, 2009 #1
    Hey all, I have a question that I'm asking on behalf of a friend.

    It is with regards to capacitors. If you had a super conductor incased in a super insulator, could you fill it to the limits of the insulation, and if there is a limit to how much charge can it can take, would the excess energy be expelled into something other then electrical discharge?

    The super conductor could be solid, liquid, plasma, or just a vacuum filled with electrons encased in a super insulator, what would be the governing limit, the material or the insulator, rate of charge can be either fast or slow dependent on stopping energy being lost via heat and vibration

    cheers,
    Rob
     
  2. jcsd
  3. Oct 21, 2009 #2
    Superconductors are very different than supercapacitors. Superconductor wire is usually wrapped in an overlapping layer of Mylar (or Kapton). Superconductors in the form of large magnets (like MRI machines), can store large amounts of energy as inductive current: E = 1/2 LI2. Sometimes a high-field superconducting magnet will "quench", meaning that a small section of the superconducting wire has gone normal. And if the magnet is not fully dicharged in a very short time, the superconductor wire will melt.
    Bob S
     
  4. Oct 21, 2009 #3
    Just a guess, but think this is simular to how x-rays are created.
     
  5. Oct 21, 2009 #4
    If you are referring to the quench of the superconducting conductor at the CERN LHC last year, it created lots of smoke, sparks, and a 14-month delay in its startup, but very few x-rays.
    Bob S
     
  6. Oct 21, 2009 #5

    berkeman

    User Avatar

    Staff: Mentor

    Nope. This is how X-rays are generally created in lab equipment (like medical and dental X-ray machines):

    http://en.wikipedia.org/wiki/X-ray_machine

     
  7. Oct 22, 2009 #6
    It sounded to me as if the questioner intended to ask a different question than the one being addressed here.
    It sounded to me as though s/he may have meant a super insulator which would never, under any circumstances, conduct electricity at all. I wonder if they had in mind a change in the nature of the energy penned up "behind" the insulator. I wonder whether they may have hoped that if the energy stored in the capacitance were sufficiently large, space itself may become bent, or a new dimension may rotate into our world, or something like that.
    Such ideas as these have become very popular among a certain set, especially since the news a couple of years ago that the theories of Heim are to be tested in the laboratory. (see the entry for Burkhard Heim in Wikipedia).
    Although I feel that this may be what the questioner intended to ask, I am certain that there are many better-qualified people than myself to answer this question on this forum.
     
  8. Oct 22, 2009 #7
    1) throw away the superconductor, it is useless.

    2) Super insulator is badly defined this word is normally used for thermal insulation

    The best electrical insulator that exists would be vacuum, although you can build more effective capacitors with a good dielectric, you can drive vacuum devices at higher voltages. The charge can then be extremely high.
    And now we are getting theoretical. I am sure that even perfect vacuum will break down at some point when the energy density is high enough to form particle anti particle pairs. But I guess long before that happens, your material metal or whatever it is cannot hold its electrons anymore. At the latest when the energy per cubic Angstrom surpasses the ionization energy for an atom. And long before that happens you have already reached the strength limit. Capacitor plates attract the more charge you put onto them. Every material will bend and break at some point.
    But to get closer to reality, at extremely high voltages you get creeping charges, surface conduction, photo effect, secondary electron emission, coronas, sharp edge emission and garbageloads of other problems.
     
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