Millikan’s Oil-Drop Experiments

Abstract

Millikan’s oil-drop experiments are justly regarded as a major contribution to twentieth-century physics [1, 2]. They established the quantization of electric charge, the existence of a fundamental unit of charge, and also measured that unit of charge precisely. As Gullstrand remarked in his Nobel Prize presentation speech, “Millikan’s aim was to prove that electricity really has the atomic structure, which, on the base of theoretical evidence, it was supposed to have.... By a brilliant method of investigation and by extraordinarily exact experimental technique Millikan reached his goal.... Even leaving out of consideration the fact that Millikan has proved by these researches that electricity consists of equal units, his exact evaluation of the unit has done physics an inestimable service, as it enables us to calculate with a higher degree of exactitude a large number of the most important physical constants” [3].¹