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Does DC Power literally travels on the surface

  1. Jan 30, 2007 #1
    Does DC Power literally travels on the surface of the wire? Compared to AC electron travel which I understand to travel within the magnetic wire used. If so, or not, can anyone make referance to some study material for clarification or a better understanding in this regard.

    Thanks for your assistance.
  2. jcsd
  3. Jan 30, 2007 #2
    No, a steady DC flow of electrons is evenly spread out in the cross section of a wire, such that to minimize the potential difference between them.
  4. Jan 30, 2007 #3
    Thanks waht, I know that it was a uneducated/silly question, but I need to varify information that is found on the net.

    Thanks again
  5. Jan 31, 2007 #4
    AC currents travel on the surface not DC. The higher the frequency the lower the penetration. You can use this to design shielding.
  6. Feb 2, 2007 #5
    Ah, that clarifies things. I understand now why 3M would use 1- 2.5 etc. micron thicknesses in their adhesive, magnetic shielding tape, i.e. 3M 9713 xyz conductive tapes.

    Is "sink effect" than sinonamous to AC current and/or is DC also effected by skin effect but to a smaller degree?

    I've often wondered if you initiate electron flow in a very thin, micron thin, closed circuit loops with a powerfull rare earth magnet(s). I understand that an equal and opposite field will be produced to repell the initiating field. As, Panda points out the higher the frequency the lower the penatration. So, is induced electron flow from a magnet/field, a low frequency? A constant influence? Can it be considered DC like? I would think that it would be a temporary but a constant(straight line) influence, direct as it were. Yes?
  7. Feb 2, 2007 #6
    You are talking about this tape right?


    The shielding is only accomplished when you surround something with a good electrical conductor. No AC EM field will escape it. This tape is loaded with conditive fibers, making it a good conductor, that's all there is to it.

    Yes a physical lorentz force will be exerted on the wire. The wire loop will move in the presence of external magnetic field. But it has nothing to do with the skin effect.

    But during the transient time, when DC current changes from zero to a constant value, an inductive effect will take place. A piece of wire with a giant magnec close by will have some inductance. That will try to oppose the DC current.

    The skin effect is where an AC current, (which flows back and forth from positve to negative) induces its own magnetic field which pulls the electrons apart. The faster they alternate, the farther apart they are being pulled in the cross section of a wire.

    Also, an AC current in a wire at a perticular frequency will induce a current in another wire closeby, at the same frequency. Skin effect once again is not really helping inducing the current in another wire.

    Hope that helps.
    Last edited: Feb 2, 2007
  8. Feb 3, 2007 #7
    Yes, Wath that is the tape I'm refering to. Just so that we all are clear of my intention. I intend to use the 3M 9713 xyz tape not for sheilding or have an AC frequency involved at all. At this time I'm confirming that there is an inherent differance between AC and a DC, relative to how they are affected by an induced magnetic field. Thus far we seem to agree that there is.

    If I may sumize what I undestand now is that an induced steady DC flow will tend to influence electrons, in a conductor, evenly spreading them out in the cross section of a wire/tape so that it minimizes the potential difference between them. So then if we use a micron filament/foil such as the 3M xyz tape in a closed loop configuration. This will also spread the potential differance accross its' y axis? And in effect cause a magnetic field that will oppose the permanet magnets' induced field? The Lorentz force you refer to. Note: The permanet magnets I'm refering to are the rare earth Neodyniums(N42), arranged in a Halbach array. I understand that this arrangement yields a field strong enough to lift 50x its' own weight. I would think that this is a very strong field eliminating the use of very large(giant), heavy permanent magnets. We also argree that an Loretz force will be exerted on the wire, in this case the 3M tape. If this conductive tape is stationary, afixed to minimize movement. Would the Halbach Array not then be moved away(repelled) by its' own induced field?

    If all holds true? How is it that I will be able to strenghten the Lorentz effect so that the resulting induced field will be able to carry the weight of the Halbach Arrays and carry 49x more? in-order to accomodate a pay-load.

    I have only looked and read on how the flux-field can be strengthened. Cooling of the medium that carries the exchange of electron flow does the trick, but this proves to be much too expensive to implement and maintain. The closest/available information is the Inductrack configuration, which I'm in the process of decifering with the limited information that's available.

    Thanks Waht, Panda

    Hey? If you find that I conclude without a clear understanding, tell me so. I would like to pursue this much futher.

    Thanks Again
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