Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Can anything conduct electricity?

  1. Dec 16, 2009 #1
    hi everyone.

    i have always been taught that there are either insulators or conductors but cant everthing conduct electricity with a high enough voltage? I know a free electron is needed to move from atom to atom to conduct electricity but if a high enough voltage is put through something does that not give a non-free electron enough energy to move to another atom?
    Last edited: Dec 16, 2009
  2. jcsd
  3. Dec 16, 2009 #2
    Well materials have valance and conduction bands. The distance between the valance and conduction band is defined as band gap. As the band gap get bigger materials become more insulator because it gets harder for to excite an electron from the valence band into the conduction band. There is another term called Fermi level which determines behaivor of materials. Aplying a voltage only changes the Fermi level not the band gap.

    So you can excite electrons from the valence band into the conduction band but at the end the conduction won't be the same as a metal. As well you might destroy materials.
  4. Dec 16, 2009 #3
    thanks for the reply.

    so the valence bands are the lower bands of the atom that the electrons populate yeah? does this mean that the amount of valence bands change with which element it is? and is the conduction band the most outer band with the least amount of electrons on and the amount of energy to move an electron from the conductive band depends on how close it is to the nucleus for example in helium there is one shell of electrons so would it take more energy to move electron in helium than radon? also does it take more energy to move electrons from a conductive band with 13 electrons than it does for a band with 1 electron?
  5. Dec 16, 2009 #4
    Air is an electrical insulator. High voltage across an air gap does not conduct electricity until the electric field is sufficient to ionize the air and create free electrons. Here is a table of ionization potentials of the elements, including helium and radon:
    Bob S
  6. Dec 16, 2009 #5
    On a related note:
    I saw an MIT YouTube footage of a thick glass rod which, when heated by a blow torch would conduct electricity.
    No practical purpose, I suppose, just a physics demo.

    Last edited by a moderator: Sep 25, 2014
  7. Dec 17, 2009 #6


    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    Please note that an electrical breakdown isn't typically considered as an electrical "conduction". So while it is true that if you apply a high enough field to almost anything, you can get charges to go across it, one typically don't consider this as an electrical conduction.

    In fact, one could get charge flow at levels well below such breakdown via field emission/field current, i.e. tunneling process. This still isn't a "conduction" in the normal sense, it certainly has more controlled aspect of the phenomenon.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook