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Induced charge on a plane

  1. Feb 25, 2012 #1
    attachment.php?attachmentid=44393&stc=1&d=1330230514.jpg
    The question itself is easy. E field at 2 is zero. E field at other points are of magnitude [itex]\frac{\eta}{2\epsilon}[/itex]

    But I am arguing with my classmate and tutor that what is the charge induced on the uncharged conductor.

    For me, I simply use the rule induced charge (charge of same magnitude but different sign will be induced) to conclude that the charge density on the bottom of the conductor must be [itex]-\eta[/itex].
    Since it is uncharged, the charge density on the top must be [itex]\eta[/itex].

    But my classmate use Gauss law and obtain that the charge density on the bottom of the conductor is [itex]\frac{-\eta}{2}[/itex].

    My tutor also said that the answer provided by professor is [itex]\frac{-\eta}{2}[/itex].

    So why I cant apply the rule of induced cahrge here?
     

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  3. Feb 25, 2012 #2
    If the charge density on the top of the uncharged conductor was η, the field in region 1 would be η/ε which is not correct.
    The rule of induced charge is applicable to grounded conductors. Here the uncharged conductor is isolated.
     
    Last edited: Feb 26, 2012
  4. Feb 26, 2012 #3
    But it seems my question is a plane.
     
  5. Feb 26, 2012 #4
    Sorry, my mistake. I edited the previous reply.
     
  6. Feb 26, 2012 #5
    Thx a lot
    I understand now
     
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