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AC Current in GHz Frequency and Zero Resistance

  1. Mar 23, 2017 #1
    Hello Experts,

    I am a physics newbie with big ideas. I have a question.
    I am thinking about how to produce a zero Resistance Current.
    We know we can do this using super-conductors in sub zero temperature, but maybe there's another way.

    My assumptions (which could be wrong):
    1) Resistance in a wire is caused by electrons traveling and HITTING other atoms as they move from proton to proton. This hitting causes electrons to lose power and transfer energy into heat.

    2) Speed of Electrons in a copper wire is about 2.5 x 10-4 m/s (2500000000nm / s)
    3) Copper Atomic Spacing 0.256 nm
    4) In an alternating current (AC), electrons are pulled back and forth typically at 60hz.

    5)
    This means:

    Time = 1 / Frequency
    Time = 1/ 60 hz = 0.166 seconds

    Which means every 0.166 seconds, our alternating current switches directions.
    Now let's talk distance:

    Distance = Speed * Time
    Distance = Speed of Electrons in a copper wire (2.5 x 10-4 m/s) * 0.166 seconds
    Distance = 2500000000nm/second * 0.166 seconds
    Distance = 416666666.666 nanometers

    Which means that a typical electron travels 416666666.666 nanometers every time our alternating current switches directions

    Now that means that our electron is hitting some protons as it travels. How many?

    Given that Copper Atomic Spacing is about 0.256 nm

    Number of Atoms Hit = Number of Copper Atoms / Copper Atomic Spacing
    Number of Atoms Hit = 416666666.666 nm / 0.256 nm = 162760416.666 copper atoms

    That' a lot of atoms to possibly hit.

    My Question:
    If we increase the frequency of our alternating current - such that an electron only traveled from 1 copper atom to another or at least some number less than 162760416.666 copper atoms. Would this not decrease the number of hits and decrease the resistance in the wire?

    Just as an example:

    Distance = Speed * Time
    0.256nm (distance between 2 atoms) = 2,500,000,000 (Speed of Electrons) * Time
    Time = 0.0000000001024 s - thats how long it takes for an atom to move from 1 atom to another

    How fast must our alternating current switch directions?
    Hertz = 1 / Time
    Hertz = 1 / 0.0000000001024 s
    Hertz = 9,765,625,000 hertz ~ 10Ghz

    So if we had a alternating current at 10Ghz, wouldn't this achieve zero resistance?
     
  2. jcsd
  3. Mar 23, 2017 #2

    cnh1995

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    Actually, ac resistance of a conductor is greater than its dc resistance due to "skin effect". Higher frequencies reduce the effective cross-section of the conductor, which increases its resistance.
     
  4. Mar 23, 2017 #3
    The resistance increases because all the electrons tend to go to the surface. More electrons in a certain space = more resistance. I get it.

    However, since we are only moving 1 atom's length of distance - they would not hit so many copper atoms.
    Additionally, since we are only moving 1 atom's length of distance, the skin effect SHOULD be minimized since the electrons have no TIME to go to the surface.

    Am I missing something?
     
  5. Mar 23, 2017 #4

    cnh1995

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    The collisions are inevitable because of the thermal motion of the electrons, which is random in nature.
    https://www.google.co.in/url?sa=t&s...jQATAl&usg=AFQjCNHa2SNZSCP6ojCffetmFmtzmdef_Q
     
  6. Mar 23, 2017 #5
  7. Mar 23, 2017 #6

    cnh1995

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    Resistance goes on decreasing with reduction in temperature. In case of superconductors, resistance abruptly drops down to zero below a certain critical temperature.
     
    Last edited: Mar 23, 2017
  8. Mar 23, 2017 #7

    davenn

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    this is incorrect .... try the other way around ... do some googling on what causes resistance

    this is also incorrect .... the electrons DONT hit the protons

    again this incorrect, see my first comment in this post .... the overall resistance of the conductor doesn't change just because you changed the frequency

    reread cnh 1995's post again --- I have hilited the important part

    and added to that there are other things that come into play when comparing AC and DC current
     
  9. Mar 23, 2017 #8
    Electrons don't 'hit' protons, they latch onto them without making direct contact and orbit around them until they are forced to move to the next atom. Also, the number of nuclei an electron moves between doesn't cause resistance. It could more accurately be seen as the difficulty of getting from one to the next.
     
  10. Mar 23, 2017 #9

    berkeman

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    This is not correct. I understand you are trying to help, but posting incorrect information is not allowed here.
     
  11. Mar 23, 2017 #10

    davenn

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    my post response deleted
     
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