Thermionic Emission

Discussion in 'General Electronics Chat' started by Mazaag, Nov 16, 2007.

  1. Mazaag

    Thread Starter Senior Member

    Oct 23, 2004
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    0
    Hi guys,

    Question here about Thermionic Emission...

    As far as I understand, when a metal is heated above a certain temperature ( does this temp have a name ? ) electrons are released from the metal to the surrounding VACCUM... however, this does not occur in air ... why is the case ? I imagine that the heat gives the electrons enough energy to break the atomic attraction to the nucleus of the atom, but how does the surround medium play a role?

    Thanks guys
     
  2. studiot

    AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    Actually it does but free electrons don't hang around long in the presence of gas molecules. They get attached to the gas molecules and get swept away by molecular motion or the molecule collides with the surface, redepositing the electron back to the metal.

    So you get a sort of dynamic equilibrium similar to that seen at a liquid/gas surface that you may have studied in the kinetic theory (of fluids).
     
  3. Mazaag

    Thread Starter Senior Member

    Oct 23, 2004
    255
    0
    I have heard something about work functions? is that in any way related ? if so , could someone explain what work function is ..

    thanks guys
     
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