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Homework Help: Determine the dielectric constant

  1. Jun 10, 2009 #1
    1. The problem statement, all variables and given/known data
    Two flat metal circles of radius r=15 mm are brought a distance d=8.0 mm apart to form a parallel plate capacitor. The surface charge density of one plate is measured to be +1.0*10^-3 microCouloubs/mm^2. The potential difference across the capacitor is measured to be .12 Volts. There is a dielectric between the plates. What is the dielectric constant.

    2. Relevant equations
    Q= CV.... maybe

    3. The attempt at a solution
    I plugged what I had into the equation, but I don't know how to find the capacitance using the surface charge density.
    I have
    C= K(8.85*10^-12)*[pi*(.015^2)/.008]
  2. jcsd
  3. Jun 10, 2009 #2


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    Homework Helper

    Find the area of the plate(mm2), then multiply that by the density to give charge.
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