Robert millikan oil drop experiment date

Experiment to measure elementary electric charge

Not to be confused with Pitch drop experiment.

The oil drop experiment was performed by Robert A.

Millikan and Harvey Fletcher in 1909 to measure the elementary electric charge (the charge of the electron).^[1][2] The experiment took place in the Ryerson Physical Laboratory at the University of Chicago.^[3][4][5] Millikan received the Nobel Prize in Physics in 1923.^[6]

The experiment observed tiny electrically charged droplets of oil located between two parallel metal surfaces, forming the plates of a capacitor.

The plates were oriented horizontally, with one plate above the other. A mist of atomized oil drops was introduced through a small hole in the top plate and was ionized by x-rays, making them negatively charged. First, with zero applied electric field, the velocity of a falling droplet was measured.

At terminal velocity, the drag force equa