# What did Milikan find in his experiment?

#### Okan

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?

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#### mfb

Mentor
1 coulomb is defined as the charge of 6.24*10^19 electrons(1 C= 6.24*10^19).
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.

#### jtbell

Mentor
1 coulomb is defined as the charge of 6.24*10^19 electrons
Where?

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.

#### Okan

Hmmm... Is that so? Well, it's senseful. Thanks.

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