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Speed of electron flow through a conductor

  1. Mar 22, 2015 #1
    Is the speed of electron flow through a conductor such as copper equivalent to 'c'?
    I've heard of this being implied several times, but is it a fact?
    I know it can't be exactly the same as 'c' because we are not talking of energy propagating though a vacuum.
     
  2. jcsd
  3. Mar 22, 2015 #2
    I'm not an expert but I know the speed of electrons in a conductor like copper is measured in cm/s.
    It's the electromagnetic field that propagates with such a speed: in fact when we turn on the light the sensation is that there isn't delay in trasmission of current.
    This fact is similar to open a tap or faucet on a pipe; a pressure wave propagates through and water, which has a smaller speed, goes out because the pipe is already full of water.
     
  4. Mar 22, 2015 #3

    Doug Huffman

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  5. Mar 22, 2015 #4
    Thanks both.
    So 'c' is not actually a relevant factor at all, although the electromagnetic field generated by a current does travel at a speed approaching c.
    (whereas the actual drift speed of electrons themselves is nowhere near c and can vary depending on various parameters).
     
  6. Mar 22, 2015 #5

    sophiecentaur

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    Furthermore, there is another mistaken idea that the energy carried is something to do with the Kinetic Energy of the flowing charges. A moment's thought should put that to bed when you consider the mass of a single electron (1/ (many thousands) of each atom) and a mean speed of a few mm/s and then think of the energy transferred by the charges in a circuit.
     
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