A New Modification of the Cloud Method of Determining the Elementary Electrical Charge and the most probable value of that Charge [ Millikan's Balanced-Droplet Experiment - Foundation for Oil Drop Experiment ]
Millikan's Balanced-Droplet Experiment

A New Modification of the Cloud Method of Determining the Elementary Electrical Charge and the most probable value of that Charge [ Millikan's Balanced-Droplet Experiment - Foundation for Oil Drop Experiment ]

London: Taylor and Francis 1910. First Edition. viii, [1]-924 pages plus 13 folding plates bound in rear. 8vo. Attractively bound in 3/4 leather over marbled boards. Marbled endpapers and page edges. A few small blemishes to the leather, bright and clean internally. Pages 209-228 contain the article "A new modification of the cloud method of determining the elementary electrical charge and the most probable value of that Charge," a key work in physics and electricity. IN The London, Edinburgh, and Dublin Philosophical Magazine, Volume XIX, Sixth Series, February 1910, pp 209-228. Near Fine. Boards. [15376]


Often falsely cited as containing "Millikan's Oil Drop Experiment", this article documents Millikan's "balanced-droplet" experiment which PREDATES his famous oil drop experiment. This paper is the first to reproducably and accurately show the unitary nature of electrical charge (which produced an accurate measurement of the charge of an electron for the first time). Experimental methods previous to his work created wildly differing measurements during repeated attempts. The balanced droplet method required the creation and use of water drops which were given an electrical charge, and then studied as they were influenced by a known magnetic field.

This paper is fundamentally important. Millikan in his autobiography notes that this paper established the "first definite, sharp, unambigous proof that electricity was definitely unitary in structure and that it only appeared in exact multiples of that unit..." effectively allowing the measurement of the electrical charge. Later work (including his oil drop experiment) refined the experimental measurement techniques and the value of the charge of an electron.

Millikan was awarded the Nobel Prize for Physics in 1923 "for his work on the elementary charge of electricity and on the photoelectric effect". Millikan showed that the charge was "always an integral multiple of an irreproducible value." He arrived at a value for e in 1909 that he considered accurate to within 2 percent. "This result provided the most persuasive evidence yet that electrons were fundamental particles of identical charge and mass". In 1913 he published the value for the electronic charge 4.774 +/- .009 x 10 (-10) e.s.u. "which would serve the world of science for a generation" " (see DSB 9/10 pp 395-396).

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