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Homework Help: Squeezing a capacitor, how does it effected the charge?

  1. Oct 9, 2005 #1
    I can't seem to get this one to work.

    Two parallel-plate capacitors, 7.0 µF each, are connected in parallel to a 10 V battery. One of the capacitors is then squeezed so that its plate separation is halved.

    (a) Because of the squeezing, how much additional charge is transferred to the capacitors by the battery?
    wrong check mark µC

    (b) What is the increase in the total charge stored on the capacitors, due to the squeezing?

    I tried the following:
    Since its in paraellel, i added the C's and got C = 14, Q = CV;
    Q = (14)(10) = 140, but they then said, the one capacitor is then squeezed so the plate seperation is halved, so I figured I would double the result i got oringally, so i'd get 140*2 = 280, which was wrong.
  2. jcsd
  3. Oct 9, 2005 #2
    Nevermind i figured it out! i just had to do 7*2 + 7, so i got (a) 70;
    But for part b, i thought it would just be 210, but it was wrong, any ideas? Thanks
  4. Oct 9, 2005 #3


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    How much MORE is 210 than 140?
  5. Oct 9, 2005 #4
    ohhh!! thanks lightgrav :) 70.
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