Electric Field from overhead lines

Discussion in 'Homework Help' started by Cerkit, Nov 14, 2012.

  1. Cerkit

    Thread Starter Active Member

    Jan 4, 2009
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    Hi. I am not too sure about the electric field from AC overhead lines, I understand an electric field from a charged particle but not too sure when there are electrons moving back and forward quickly as in AC what the field looks like??
    Can someone please explain to me what the electric field from overhead lines looks like, is it just away from the conductor core radially (can anyone refer me to a diagram for this) and why is it so. Is the electric field alternating ? Do you need current to flow for the field to exist or does it exist just with a potential?
     
  2. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    Here are the graphics
     
  3. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    Yes, because the voltage is alternating.
     
  4. Cerkit

    Thread Starter Active Member

    Jan 4, 2009
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    Ok. So would it be correct to say that there is an electric field (albeit weaker) a fair distance away from a current carrying conductor because of the electromagnetism? Would it be correct to view it like that in the sense that the electric field exists as a result of the propagation of the magnetic field surrounding the conductor?
    I guess the concept of the electric field existing a certain distance away from a conductor is just hard to understand intuitively.
     
  5. crutschow

    Expert

    Mar 14, 2008
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    Not really.

    Magnetic fields are generated by current flow in a wire and are proportional to the amount of current.

    Electric fields are generated by and are proportional to the potential (voltage) in a wire and are independent of current or the magnetic field.

    Both decrease with distance from the wire.

    If the voltage in a wire is alternating, then so will the associated electric and magnetic fields.

    Of course an alternating electric and magnetic field also generates an electromagnetic (radio) wave which propagates through space to a much greater distance then the magnetic and electric field do.
     
  6. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    But magnetic fields are a lot harder to shield......:mad:
     
  7. Cerkit

    Thread Starter Active Member

    Jan 4, 2009
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    Ok. But what actually constitutes of the electric field, how does the electric field exist lets say several metres away from the overhead line, if I hypothetically placed an electron a few metres away from the overhead line what (is the physics behind it that) makes the electron to be pushed/pulled according to the electric field??
     
  8. takao21203

    Distinguished Member

    Apr 28, 2012
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  9. MrChips

    Moderator

    Oct 2, 2009
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    Sometimes we pull up our sailboats on to a beach where there are HV transmission lines very high overhead. I talking about those huge power transmission pylons.

    If you were to touch the metal masts or stays of the sailboats you would get an electrical shock.
     
  10. Cerkit

    Thread Starter Active Member

    Jan 4, 2009
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    But what actually constitutes of the electric field, how does the electric field exist lets say several metres away from the overhead line, if I hypothetically placed an electron a few metres away from the overhead line what (is the physics behind it that) makes the electron to be pushed/pulled according to the electric field??
     
  11. MrChips

    Moderator

    Oct 2, 2009
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    Google Maxwell's Equations.
     
  12. crutschow

    Expert

    Mar 14, 2008
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    I'm not sure what you mean by "how does the electric field exist". It exists by virtue of the electrons in the wire and the charge on each electron. It has been experimentally determined by numerous experimenters that an electron generates an electric field in it's vicinity which decreases with distance from the electron. In a conductor, the field is proportional to the voltage between the conductor and ground. Also this electron field repels other electrons, thus a negative electric field from an excess of electrons will repel electrons (otherwise all the electrons in the universe would be lumped together in one very large sphere).

    If you want to know why or how an electron generates an electric field that's getting into metaphysics (or perhaps string theory, I'm not sure which).
     
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