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What did Milikan find in his experiment?

  1. Nov 16, 2014 #1
    Hi guys. I was searching about electricity lately and noticed something: Milikan determined the charge of an electron as 1.602*10^-18 coulomb(1 e=.1.602*10^-18 C). If he used the unit "coulomb" in his work, coulomb must exist in his times. 1 coulomb is defined as the charge of 6.24*10^19 electrons(1 C= 6.24*10^19). If i take the reverse of (1 C= 6.24*10^19), i get (1 e=.1.602*10^-18 C). In conclusion there was no need to do the oil drop experiment to find the charge of one electron if one coulomb was already defined in his times. Where am i wrong? Which is older, the definition of C or the oil drop experiment?
  2. jcsd
  3. Nov 16, 2014 #2


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    Staff: Mentor

    It is not. This is actually a planned definition (just with more precision), but currently and historically the Coulomb had/has different definitions. At that time they did not even know about electrons.

    By the way, Coulomb died around 1800, Millikan did his famous experiment in 1910.
  4. Nov 16, 2014 #3


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    One coulomb is currently (pun! :p) defined as the quantity of charge carried by a current of one ampere in one second. The ampere is defined in terms of the magnetic force between two current-carrying wires. These definitions have evolved over time, and I don't know the exact definitions Millikan used.
  5. Nov 16, 2014 #4
    Hmmm... Is that so? Well, it's senseful. Thanks.
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