Measurement of the elementary charge (oil-drop experiment)
Medida de la carga elemental (gota de aceite)
- Date
- 1909-1913 · confidence high
- Place
- University of Chicago, United States
- Credited to
- Robert Millikan; Harvey Fletcher
- People
- 👤 Harvey Fletcher1884–1981👤 Robert Andrews Millikan1868–1953
- Field
- Matter & energy
⚠️ Disputed: the sources disagree.
What was discovered
Observing charged oil drops suspended in an electric field, Millikan demonstrates that charge is always a multiple of an elementary unit and measures its value. Electric charge is quantised.
Fletcher, a doctoral student, contributed decisively without appearing as a co-author; Millikan's data selection has been criticised.
What it led to
- Precise value of e and, with e/m, the electron's mass
- Planck's constant via the photoelectric effect (1916)
- Foundation of quantitative electronics
- Definition of the ampere by e (2019)
Built on
- Thomson's electron
- Wilson's cloud chamber method
Made possible
- Precision electrical metrology