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Excess or deficit electrons.

  1. Oct 28, 2013 #1

    Zondrina

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    Homework Helper

    1. The problem statement, all variables and given/known data

    A small plastic sphere is suspended between two parallel plates like so: http://gyazo.com/0b5425a78b645d85da0b3475d6d71734

    How many excess or deficit electrons does the sphere have?

    2. Relevant equations

    ##m=2.60x10^{-15}kg##
    ##V=265.4V ##
    ##d=0.500cm=0.000500m=5.0x10^{-4}m##
    ##g=9.81m/s^2##

    ##q = \frac{mgd}{V}##

    ##q = Ne##
    ##e = 1.6x10^{-19}C##

    3. The attempt at a solution

    The charge on the sphere is clearly positive because it is suspended in mid air and I calculated the magnitude of the charge to be ##q=4.8x10^{-20}C##.

    This confused me slightly. Solving for the excess/deficit electrons ##N = 0.3##.

    How can the sphere have a fraction of a deficit of electrons? I thought ##N## could only be an integer.
     
  2. jcsd
  3. Oct 28, 2013 #2

    gneill

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    Staff: Mentor

    Check your conversion of d to meters.
     
  4. Oct 28, 2013 #3

    Zondrina

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    Whoops, I forgot a zero there ##d = 5.00x10^{-4}m##.

    This doesn't really change the answer though.

    EDIT : Ohhh I have an extra zero -facepalm-

    I got it now thanks!
     
  5. Oct 28, 2013 #4

    gneill

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    Staff: Mentor

    :smile:
     
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