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Electric fields and Frozen charges

  1. Feb 20, 2009 #1
    Electric fields and "Frozen charges"

    1. The problem statement, all variables and given/known data
    A large parallel plate capacitor is charged at first and creates a uniform electric field inside which is to the right and of magnitued E0. Then a small metal box is inserted inside the capacitor; small means that the insertion does not modify the charge distribution on the capacitor. This will make the field inside the metal box zero (Faraday cage). Now imagine you could somehow freeze or nail down all charges in the entire system and then remove the metal box with all its frozen charges far away from the capacitor.

    Draw a picture that shows what the electric field looks like 1. inside the hollow of the box, b. inside the body of the box, and c. outside the bow. (THe principle of superposition is helpful).

    3. The attempt at a solution
    My first thoughts when I saw this were that you would generate an electric field going from one side of the box to the other. But...since the box is metal (so a conductor), the charges would rearrange themselves and the box would become neutral, and there would be no electric field. Would there?

    Also...it says that the charges are frozen...would you take this to be that half of the box remains positively charged and half of it remains negatively charged? If so, how would you draw that...lines curving inward from one side inside the gap? and outward on the outside?
    This might be asking a bit much...I could try to post the original image but I'm not sure how.
  2. jcsd
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