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Homework Help: The total force on a charge plate

  1. Dec 27, 2011 #1
    Three boards are in the x axis. the middle one is in x=0 and charged in a positive sign density is: σ. the other 2 boards are in : x=d and x=-2d. This 2 boards are grounded. The area of the boards is A (A>>d).

    I found that on the middle plate the charge is divided in 2:1 ratio: The electric field from X=0 to X=d is:E1 = (8/3)*∏*k*σ
    and from X=0 to X=-2d is: E2 = (-4/3)*∏*k*σ.
    If I want to find the total force on the middle plat should I do: F=σ*(E1-E2) ?? I get (4/3)∏*k*(σ^2)*A

    but the answer says: F=(2/3)∏*k*(σ^2)*A

  2. jcsd
  3. Dec 29, 2011 #2


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    Homework Helper

    See your other thread with the same problem.

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