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Homework Help: Parallell plates

  1. Jul 31, 2008 #1
    1. The problem statement, all variables and given/known data

    I have two parallell plates, they are separated a distance of 1 cm. The potential difference is 10kV. A 0.5 cm thick plastic plate lies between the two plates and has a relative permitivitty of 6. Calcualte E and D in the air and in the plastic plate.

    2. Relevant equations



    3. The attempt at a solution

    D is the same for air and the plastic plate

    The electric field without the plastic plate is [tex] E = \frac{p_s}{e_o} [/tex] and [tex] D = p_s [/tex] but [tex] E = \frac{V}{d} [/tex] that means that [tex] P_s = \frac{V*e_o}{d} = D [/tex] but thats not the right answer for D.

    I get D = 8.85e-6 but it should be 1.5e-5
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Jul 31, 2008 #2
    You can treat this as two capacitors in series: one for the air part and one for the plastic part.
     
  4. Jul 31, 2008 #3
    hmm ok..but how do I start whit the calculations then? and isnt it possible to calculate the electric flux D and go from there?
     
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