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What is the potential difference between the plates?

  1. Feb 6, 2004 #1
    Here's my problem:
    A parallel-plate air capacitor has a capacitance of 730 picoFarads. The charge on each plate is 2.95 microCoulombs.
    a) What is the potential difference between the plates? I used the equation V=Q/C to get 2.4746E-4 V, but this is incorrect.
    b)If the charge is kept constant, what will be the potential difference between the plates if the separation is tripled?
    I think it would be divided by three.
    c) How much work is required to triple the separation?
    U=1/2 Q V

    I think if I could calculate the potential difference correctly, I could work the rest of the problem. Any hints/help would be welcome!!!
  2. jcsd
  3. Feb 6, 2004 #2


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    Check your arithmetic, I do not get the result you posted using the same equation and numbers. Post your calculation.
  4. Feb 7, 2004 #3
    I punched the numbers into the calculator wrong! I now get the voltage equal to 4041.1
    Tripling the distance produces a voltage of 3V or 12123.3
    Now, how do I apply the equation U=1/2 Q V to find the work required to triple the separation?
  5. Feb 7, 2004 #4
    it would be Uf-Ui=W
  6. Feb 7, 2004 #5
    Thank you!!! You are all so helpful :)
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