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Homework Help: The Millikan Oil Drop Experiment (calculating e given a series of charges)

  1. Feb 26, 2008 #1
    1. The problem statement, all variables and given/known data
    This is a lab, where we have to calculate the constant e (1.602e-19 C) by calculating the terminal velocity of an oil drop while under the influence of gravity, and the terminal velocity while under the influence of gravity and a known electric field.

    2. Relevant equations
    Eq - W = W(v2/v1), where v2 is the terminal velocity with the E field and v1 is without. W is the weight of the oil drop (mass * gravity of the drop), E = V/d is the electric field. Solving for q:

    q=W(v2/v1 + 1)d/V

    Weight is calculated with a series of other equations.

    3. The attempt at a solution
    The goal is to ?quantitize? the charge found on a series of drops. I found the charge for three drops to be:
    4.678E-16, 6.367E-16, 4.32616E-16

    These values must be some value x multiplied by an integer n, where x will turn out to be 1.602e-19 C. The problem is I don't know how to find this value given 3 values of charge for three different oil drops. Also, these seem to be very large numbers. These oil drops are very small, and in the lab they should typically vary between n=1 and n=10, from what I've read. So what should I do? If you plot three functions from the above, they are just contours and so don't cross.
  2. jcsd
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