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Homework Help: Change in Voltage

  1. Feb 6, 2010 #1
    1. The problem statement, all variables and given/known data
    Why is the change in voltage between two capacitors V=ED ?

    2. Relevant equations

    3. The attempt at a solution
    Isn't the change in voltage equal to the negative of the product of the electric field and displacement?
    So, why is it that for a capacitor the change in voltage is not V=-ED ?

    Thanks for any help.
  2. jcsd
  3. Feb 6, 2010 #2
    The flow of electrons through a capacitor is directly proportional to the rate of change of voltage across the capacitor, but in the case of resistors it is directly proportional to the voltage drop.. from there it appears the difference.. at least thats what I think :)
  4. Feb 6, 2010 #3


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    Homework Helper

    There is some confusion when speaking about voltage. Some people call the electric potential "voltage" others define voltage as potential drop. According to Ohm's law, the current I causes a potential drop - voltage- across a resistor R, equal to V= IR, but the electic potential changes by -IR in the direction of the current.
    Between the capacitor plates, the potential U changes by -ED in the direction of the electric field, that is from the + plate to the - one, and by + ED in the opposite direction. Or you can say that the potential of the positive plate is by ED volts higher than the potential of the negative plate.

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