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Homework Help: Calculating the capacitance of a parallel-plate air capacitor

  1. Feb 16, 2013 #1
    1. The problem statement, all variables and given/known data
    A parallel-plate air capacitor is made by using two plates 18 cm square, spaced 3.5 mm apart. It is connected to a 3-V battery.

    What is the capacitance?

    2. Relevant equations

    C = εo(A/d)

    3. The attempt at a solution

    εo = 8.854e-12
    A = .18 m
    d = .0035 m

    C = εo (.18/.0035) = 4.55348571e-10 F

    This is coming up as the wrong answer. I have no idea what I'm doing wrong.
  2. jcsd
  3. Feb 16, 2013 #2
    Never mind, I solved the problem. I read "18 cm square" to mean 18 cm2, but I guess it really meant a square with 18cm sides, so A = .0324 m2. Sorry about that!
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