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Millikan Oil Drop Issue

  1. Aug 6, 2012 #1
    I completed the Millikan oil drop lab in class with as much accuracy as possible. I used the PASCO interface and used a very accurate Air pressure calibration. My final experimental charge of the electron derived from the equation in the lab was, 1.8 x 10 ^-19 C. When I turned in my lab, I was docked points for having a "very rare" one electron on the oil drop analyzed even though the percent discrepancy is something like 12.5 percent compared to the theoretical charge of the electron. Would I be wrong to contest this?

    edit- usually the charge contained on one drop is due to several electrons and dividing by the theoretical charge gives you how many electrons are on it. I got one electron on the drop and got docked
    Last edited: Aug 6, 2012
  2. jcsd
  3. Aug 6, 2012 #2
    how much cahrge did you get on a drop...if it was only 1.8 x 10-19C then it looks strange because that is close to exactly 1 electron
  4. Aug 6, 2012 #3
    That is the exact computed number from the equation
  5. Aug 6, 2012 #4
    wow..that is strange, sounds like you had a drop with exactly one electron on it.
    Not impossible but also not likely.
    Did you have lots of measurements on drops to get a final answer?
  6. Aug 6, 2012 #5
    Took 6 times up and 6 times down averages them separately and computed from there
  7. Aug 7, 2012 #6


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    Staff: Mentor

    If I remember correctly, in this experiment I had 2 drops with a single electron, too. 2 out of ~30, with most somewhere in the range of 2-10 electrons.

    You cannot measure the elementary charge with a single drop only. How many electrons did you have in the other drops?
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