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Photons and electrons and electricity.

  1. Apr 16, 2013 #1
    A) I want to understand electricity in terms of quantum theory.
    as I understand photons are the carriers of EM energy so
    how do photons trasfer energy from electric company or battery through a wire.
    and the connection to electron movement (do electrons from one atom bum into another electron in
    another atom)
    how is it different in cases AC and DC what is the directionality of photons and electrons.

    B) current in wire causes heat, so what exactly causes it,in cases of good conductor and bad
    conductor.
     
  2. jcsd
  3. Apr 16, 2013 #2

    ZapperZ

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    You DO know that such a topic covers whole chapters of books on Solid State Physics, don't you?

    Maybe I can give you a simpler start. If you wish, you can look up the Drude Model. This might be an easier way to introduce you to charge transport in solids. Try to understand that first, and come back and ask questions here if there's something you don't understand.

    Keep in mind that when atoms form a solid, they lose a lot of their individual characteristics. The energy levels that are typical for an atom is now gone (at least at the low energy range), and all the atoms collectively form "bands" of energy. That's why you have the conduction band and the valence band, and why we have energy gaps in semiconductors/insulators.

    Zz.
     
  4. Apr 16, 2013 #3
  5. Apr 24, 2013 #4
    Electrons transfer energy through a wire.

    Absolutely. This is called electron scattering.
     
  6. Apr 25, 2013 #5
    I was not aware of that.
    I wiil read what ou directed me, does solid state cover electric transfer via lighting through air to the ground ?
    I also thought of some high level regarding trsnfer/exchange of of photons to get general picture or I'll just stick to what you directed me?

    thankx a lot
    I have a lot of study to cover:)
     
  7. Apr 25, 2013 #6
    no. air is not a solid.
     
  8. Apr 25, 2013 #7

    thankx for the reply.
    I want to know how energy transfer is done through photon even when no wire
    like in tesla coil or lightning.
     
  9. Apr 25, 2013 #8
    soilid, air, or fluid.

    whether ions flow in liquid or lightning in the air or electrons in a solid wire.
    I want to know how EM energy/photons are transferred
    the big picture and reference to details(solid state already got)
    thankx.
     
  10. Apr 25, 2013 #9
    lightning is just a name we have given to a rapid electric breakdown of air it doesn't flow.The ions do yes.

    Well quite honestly I think for starters you are asking very complicated questions which hardcore scientists themselves don't even know all the time.

    Speaking about the flow of electricity there are two main things, one is the flow of charge , which is the actual flow of electrons at a given point and measures in Amperes.This is called current and it is responsible for the work that is done by electricity when it flows through a circuit.

    Then there is voltage written as V and V describes the potential difference between two points.
    Like rub your clothes against your hair and the hair and clothes will be set at a higher potential than ground so charge will be accumulated and once you will provide a path for it to flow a simple circuit will be formed and the potential difference will be lost due to charge flowing from the point of highest potential to the one of lowest.

    Now if you wonder why electricity moves so fast and why actual electrons move so slow then your mentioned photons come into play.The actual electrons move slowly but once one of them is excited(current applied to a wire) it emits a photon which travels a the speed of light to hit the next electron and excite it so that it could move on to get the next one.Ofcourse there are billions of these interactions in a EM field and Em field itself propagates at c in vacuum and close to c in typical mediums like air around us.
    This is the reason why when you listen to radio you here the news of today rather than the ones of yesterday.
     
  11. Apr 25, 2013 #10
    thankx alot I'm beggining to undestand.
    last question if you may,
    why photons seem to have ( I think) a strait directionality whether electrons flow in one direction (DC), or changing direction(AC) , eventualy we get them at home from the electric company.
    ( I would expect photons to change direction with the current direction.
     
  12. Apr 25, 2013 #11
  13. Apr 25, 2013 #12

    http://en.wikipedia.org/wiki/Lightning

    The voltage [electrical potential] build up causing ions [charged particle] to form and these are able to conduct electricity...it's a type of 'insulation breakdown'.......

    Separately, you may find a bit of reading about plasma of interest:

    http://en.wikipedia.org/wiki/Plasma_(physics [Broken])

    The first part is true; the second part is true, but in my opinion are rather unrelated. A plasma is not a unique fourth state of matter because it is electrically charged: if that were true, semiconductors would also be classified as a 'plasma'...and electrons as well....


    Regarding current in a wire:

    Crazymechanic posts:

    I've never seen such a description involving photon emission. I don't believe photon emission is required. [Edit: I take that back....it's a quantum field theory perspective...It's not required in a classical discussion with fields and electrons.]

    An easy way to visualize electron flow is like cars getting on a highway....when it is crowded [lots of conductors] one car can't get on here until all the cars move along there. Likewise, electrons repel each other and are pushed along by a potential. Equivalently, you can say the electric field moves all the free electrons along equally. The flow of ions, say in an electrolyte in battery or in salt sea water [electrolysis or galvanic corrosion] move along in like manner.....no emission of photons is required there either. The field effects move close to the speed of light, but the electrons in a conductor move at a much slower DRIFT velocity.

    Dr Zoidberg has some good insights here:

    https://www.physicsforums.com/showthread.php?t=683365&highlight=electric+current+flow


    For some views on quantum mechanics and electricity:
    http://en.wikipedia.org/wiki/Semiconductor
     
    Last edited by a moderator: May 6, 2017
  14. Apr 26, 2013 #13
    """why photons seem to have ( I think) a strait directionality whether electrons flow in one direction (DC), or changing direction(AC) , eventualy we get them at home from the electric company."""

    I'm sorry for taking this to deep , by the way you don't know where photons travel , only when you measure one you can say something about it.
    Also the electrons in your home wall socket do not come from the power company they actually have been there all the time in your wire.
    Especially considering AC the net drift of electrons is zero because they oscillate back and forth with the frequency would it be 50 or 60 hz depending on the country you live in.
    So actually the electrons you get in your house have been there all the time in the circuit boards , cables and all other conductors attached to the wall socket.You just can't use them unless they flow in a flow of electrons which they do because current is applied to the cable at the power station all the way to your house.
     
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