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Homework Help: Find the area of the plate

  1. Dec 15, 2012 #1
    1. The problem statement, all variables and given/known data

    platearea.jpg

    2. Relevant equations
    capacitance = charge/volt

    capacitance = Esub0 (side of parallel plates^2)/(distance apart)




    3. The attempt at a solution

    capacitance = (3*10^-6 C)/(150v)
    capacitance = 2 * 10 ^ - 8 F

    2 * 10 ^ - 8 F = (8.85 * 10 ^ -12)(side of parallel plate) ^ 2/(.90 *10^-2)

    side of parallel plate is 20 m ^ 2.
     
    Last edited: Dec 15, 2012
  2. jcsd
  3. Dec 15, 2012 #2

    gneill

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    Staff: Mentor

    Your distance value doesn't look right; check your units conversion. Since you're looking for the plate area anyways, why involve the square of the side length when you can solve directly for the area?

    Fix your d value and try again. Make sure that your result description and units match (you reported a side length in square meters before).
     
  4. Dec 15, 2012 #3
    oops milli is 10^ -3

    i found my mistake. plate area = (capacitance)(distance)/(esub0)

    plate area = (2*10^-8)(.90 * 10 ^-3)/ (8.85 * 10 ^ -12) = 2 m ^ 2 =]

    thanks gneill
     
  5. Dec 15, 2012 #4

    gneill

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    Staff: Mentor

    Yup, that looks better :smile:
     
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