Millikan's Oil Drop

-Steve M, Anna, Ellie

The Oil Drop Experiment, originally developed by Robert Millikan, had the aim of measuring the electric charge of a single electron, by using charged electric plates. Millikan measured the electrical charge of electrons. He completed his experiment in 1909, and by 1913 he had refined his experiment, and had a highly accurate measure of the charge of an electron. Originally, he sprayed droplets of water through an electrical field that was intended to suspend them in midair, but the water droplets evaporated too fast, so Millikan switched to using oil.

From: http://honolulu.hawaii.edu/distance/sci122/Programs/p28/p28.html

Millikan set up his expiriment by spraying oil drops, which would fall between a positively charged plate and a negatively charged plate. He balanced the electric charge with the electron's weight, as gravity pulled down on the oil drop, and the electric charges attracted and repelled it. Using this method, Millikan discovered that the charge of an electron is negative. The weight of each drop was determined by observing it's rate of free fall through the air (McGraw 302). As a result of this experiment, It Is know known that the electrical charge of an electron is negative.

From: http://chem.ch.huji.ac.il/~eugeniik/history/millikan.html

Millikan measured that the charge of an electron was 1.602 E-19 (Delpierre, G.R. and B.T. Sewell). He knew that the electrons were negatively charged because of the charge of the plates and how the oil drops were repelled from the negative charge.

scientists have also used Millikan's oild drop to look for free quarks. They have so far been unsucessful ("Oil-Drop Experiment").

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