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Homework Help: Oil drop

  1. Jan 17, 2010 #1
    Oil drop weighs 5.8 x 10^(-15)N. It is suspended in a uniform field produced by a pf of 363V between 2 parallel plates 6cm apart.

    1. Calculate charge on drop.

    2. How many excess electrons does it carry?

    My question is, why are the electrons excess? The answer is 6, which is basically the answer to 1 divided by the charge of an electron. Why are all the elctrons excess?
  2. jcsd
  3. Jan 17, 2010 #2
    In a neutral drop there would be an equal number of positive (proton) and negative (electron) charges.
    For the drop to be charged, there must be more - than +. Hence the term "excess".
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