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Conductors and fields

  1. Feb 22, 2009 #1
    I had been reading Feynmann lectures , and in it he has shown an argument which proves that E field inside an empty cavity of a conductor is zero_OK. Now he says a similar argument can be used to show that if there is some charge in a cavity of a conductor than the field outside must be zero. Electrostatic shielding works both ways. Doubt: But then if we consider a gaussian surface containing the conductor , then the net charge is not zero => integral(E.da) is non zero, but E is zero. HOW?
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  3. Feb 22, 2009 #2


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  4. Feb 23, 2009 #3
    How does grounded-ness preserve the argument?
  5. Feb 23, 2009 #4


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    If the conductor is grounded, an amount of charge equal and opposite to the amount in the cavity can come into the conductor and the net charge inside a Gaussian surface containing the conductor would be zero. Of course this doesn't necessarily mean E must be zero, but it turns out that under electrostatic conditions the charges always rearrange themselves such that it is.
    Last edited: Feb 23, 2009
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