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Conductor question

  1. Feb 1, 2008 #1
    Do in conductor (like Cu wire) have electron holes, like there is in the semi-conductors?
     
  2. jcsd
  3. Feb 1, 2008 #2

    Ben Niehoff

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    It depends on the conductor, but in metal conductors, it is generally the electrons that are free to move.

    You can experimentally determine whether the charge carriers are positive or negative by means of the Hall effect.
     
  4. Feb 1, 2008 #3
    But still they are in their orbitals, so anyways they'll make gap, right?
     
  5. Feb 1, 2008 #4

    chroot

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    An ionized metal atom is a "hole" just like an ionized semiconductor atom, but the energies involved are much, much smaller, and therefore pretty much negligible.

    A hole in a semiconductor requires an electron to be promoted across a band gap -- from the valence band to the conduction band -- and these band-gap energies are pretty large. In contrast, some electrons are always in the valence band in metals, so they're always free to move around. There's no band gap to overcome, and thus no large energies involved.

    - Warren
     
    Last edited: Feb 1, 2008
  6. Feb 1, 2008 #5
    Will the gaps move in the conductor? Why you think that in semi-conductors there must be more energy to excite the valence electrons, and thus jumping off the orbital, leaving gap?
     
  7. Feb 1, 2008 #6

    chroot

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    Metals don't have a band gap. Their outermost electrons are always in the valence band, which makes them easy to move around without requiring much energy.

    I'm not sure what you mean by asking "why" I "think" something.

    - Warren
     
  8. Feb 1, 2008 #7

    Ben Niehoff

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    He's conflating the terms "band gap" and "hole", is all, Chroot.
     
  9. Feb 1, 2008 #8
    Sorry, I thought for the holes. Is there any holes in the conductor? Do they move like in semi-conductors? I know that also the "free electrons" are staying in some orbital. So when they'll leave it, they leave holes, right?
     
  10. Feb 1, 2008 #9

    chroot

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    I believe I've already answered this.

    The concept of a "hole" in a semiconductor is the ion left behind when you promote an electron through the (fairly large) gap between the valence and conduction bands, and the electron moves away. This promotion requires a good bit of energy. The same amount of energy is released when another electron drops back out of the conduction band and fills the hole. (This is called recombination.)

    In metals, there is no band gap, and some electrons are perpetually in the conduction band. No promotion is necessary. It still requires some tiny amount of energy to ionize a metal atom, but the energy is so small that it is negligible. Thus, the concept of a "hole" is not very useful for metals.

    - Warren
     
  11. Feb 1, 2008 #10
    But there will be many more holes in the conductors, and not in pure semi-conductors, lets say like sillica, right?
    Also I have one more question. When the electrons get away from the orbital while there is current, they jump from orbital to orbital, or they move in the space, not in the orbitals?
     
  12. Feb 1, 2008 #11

    chroot

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    I don't know what you mean. As I've said repeatedly, the concept of a "hole" does not really apply to metals.

    I have no idea what you're asking here either. Orbitals do not have sharp boundaries, and can overlap even over a distance.

    - Warren
     
  13. Feb 1, 2008 #12
    I want to ask you what happens when there is current. The electrons jump from orbital to their neighbor's atoms orbital, or?
     
  14. Feb 1, 2008 #13

    chroot

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    Yes, this is a good way to think of it. Actually, it's even more effective to think of the free electrons in a metal as comprising a "free electron gas." In many respects, the conduction electrons behave as if they're a free gas, since the energies involved in "joining" and "leaving" any particular atom are so tiny.

    - Warren
     
  15. Feb 1, 2008 #14

    ZapperZ

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    There are no more "orbitals" here. The conduction electrons are not localized to any atom. That's why I keep saying that in solid, in many cases, the typical property of the solid has nothing to do with the property of the individual atoms any more. The atoms that make up the solid has lost most of its individual identity.

    All you need to do to convince yourself of this is the fact that conductors have conduction bands, which is a continuous band that these electrons occupy. Individual atoms have no such bands. So obviously, these electrons have formed something that individual atoms cannot ever form. This is the clearest indications that a solid is different than an atom.

    As Phil Anderson likes to say, More Is Different.

    Zz.
     
  16. Feb 1, 2008 #15
    Sorry if I am repeating the same question again, but I think I still didn't understand the answers. When current flows, the electrons jump from orbital to their neighbor's atom orbital, or they are just moving free outside of all of the orbitals of the atoms?
     
  17. Feb 1, 2008 #16

    ZapperZ

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    I give up. I have no idea how to make that any clearer.

    Zz.
     
  18. Feb 1, 2008 #17

    chroot

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    Orbitals do not have sharp boundaries; they technically extend to infinity. An electron can be a hundred miles away from an atom and still exist in an orbital. In fact, an electron can exist in many orbitals of many atoms simultaneously. It does not make sense to think of electrons as hopping from one orbital to another in a sequential fashion.

    Think about the electrons in metals as comprising a free electron gas, and you'll have a much better mental model of how conduction occurs.

    - Warren
     
    Last edited: Feb 1, 2008
  19. Feb 1, 2008 #18
    Ok, thanks.
     
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