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Homework Help: Parallel Plate Capacitor

  1. Mar 5, 2010 #1
    1. The problem statement, all variables and given/known data

    A parallel plate capacitor is made of two circular disks. The distance between the disks is very small compared to their diameter. Initially, the disks are electrically neutral. After transferring 3.9x10^9 electrons from one disk to the other, the electric field strength in the space between the plates is 1.0x10^5 N/C. What is the diameter of the plates?

    e = 1.6x10^-19C

    2. Relevant equations

    3. The attempt at a solution

    I was able to calculate the charge on the plates by multiplying the number of electrons by their fundamental unit charge:

    3.9x10^9 * 1.6^10-19C = 6.24x10^-10C

    However I'm really lost as to what to do next. Any guidance would be much appreciated.
  2. jcsd
  3. Mar 5, 2010 #2


    User Avatar
    Homework Helper
    Gold Member

    Can you find or derive an equation that gives the electric field of a uniformly charged plate or plane? An equation relating to a capacitor might help.

    If you can't find an existing equation, Gauss' law can help you derive it (given that the problem states "distance between the disks is very small compared to their diameter").
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