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Homework Help: Electric field over a non-conducting disk in term of ε0

  1. Oct 4, 2012 #1
    1. The problem statement, all variables and given/known data

    A non-conducting disk with a 4-mm thickness is lying flat. It has a -4 C/m^2 surface charge on the upper surface and a surface charge on the lower surface. In terms of epsilon naught, what is the approximate field strength 1 mm above the upper surface?

    2. Relevant equations

    E(disk)z = η/2ε0 * [1- ( z /√(z^2 +R^2)) ]
    3. The attempt at a solution
    The radius R and charge are unknowns, I have no idea how to aproach this problem, Im stuck. I would like some help to interpret the known data so I can start to build an answer! Please, and thanks in advance for any suggestions.
  2. jcsd
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