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Question about lightning

  1. Jul 20, 2007 #1
    What happens to the electrons in the lightning after they hit the earth soil? After these so many lightning hits the earth, won't there be excess of electrons in the earth? How do these electrons escape from the earth?
     
  2. jcsd
  3. Jul 20, 2007 #2
    Lightning equalises the potential between earth and sky (think of it as neutralising the earth), so a good question would be "what causes the excess of charge that will result in the lightning?"

    According to the howstuffworks website (hint: google "lightning"), "The upper portion of the cloud is positive and the lower portion is negative. How the cloud acquires this charge is still not agreed upon within the scientific community".
     
  4. Jul 20, 2007 #3
    I went through the url http://www.glenbrook.k12.il.us/GBSSCI/PHYS/CLASS/estatics/u8l4e.html as well as the howstuffworks website. This gives me few more questions.

    1. When the lightning start from the lower portion of the cloud, why can't it traverse to the upper portion of the cloud (instead of to the earth) which is geographically much closer than the earth's surface.

    2. As per the web sites, "... the electrons at the earth's surface are repelled deeper into the earth by the strong negative charge at the lower portion of the cloud. This repulsion of electrons causes the earth's surface to acquire a strong positive charge..."
    I would imagine, the electrons that were part of the earth's soil did move away from those silicon atoms, either laterally or deeper. And the electrons from the lightning filled those atoms to neutralise. But what happens to the old electrons in the earth's surface, that were repelled by the cloud's negative charges?

    Shouldn't these excess electrons create a lightning from earth to outside of earth?

    3. Lightning happened, the electrons from the lower cloud got discharged to the earth. But what happens to the positive charges in the upper part of the cloud?

    The circuit looks incomplete to me.
     
  5. Jul 20, 2007 #4
    Who says there has to be a circuit? You can easily shunt charge around in a non-conservative fashion if you cheat. The charge imbalance in the thundercloud doesn't have to go back into the thundercloud, in fact this is what lightning is; electrons from the cloud discharge into the ground because this is presumably the lowest potential energy state for them. Because the Earth has a vast charge density compared to the cloud, it's much more realistic to dump the extra charge from the cloud into the soil than keep it all in the cloud. Yes, the earth will probably be slightly charge-imbalanced afterward, but it can take it.
     
  6. Jul 20, 2007 #5
    I've read about an old electrostatic generator that makes 2 feet sparks(maybe several hundred thousand volts). The generator is unique from other 'friction' or induction types of generator that it simply uses a smooth metal plate, on which steam from a boiler or steam generator rapidly condenses.

    I no longer have a link, but it may be found on google. It may be no coincidence that in cumulonimbus clouds, rapid condensation is also ocurring.

    Just something to share to anyone not aware with such electrostatic generator ;)
     
  7. Jul 20, 2007 #6

    mgb_phys

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    It usually does - lightning strikes within clouds are much more common than strikes to earth, especially at high altitude. But because they are inside the cloud you don't always see them, when you do it's called sheet lightning because it lights up the entire cloud like a white sheet.

    When something gets a charge it is only a tiny fraction of the atoms that are affected. There are an awfull lot of atoms in the Earth - so a few extra electrons in a small area under a lightning strike can easily be absorbed.

    If there was anything oppositely charged outside earth and near enough - yes. The trouble is that vacuum is a rather good insulator.
     
  8. Jul 20, 2007 #7

    ranger

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    This is the case with Venus. The lightening strikes never hit the Venusian surface. Instead there is cloud-to-cloud lightening which is weaker than terrestrial lightening. Remember that the atmosphere of Venus is extremely dense when compared to the earth.
     
  9. Jul 20, 2007 #8
    Any answer to this question?
    In other words, what happens to the cloud after it created the lightning?
     
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