One important result of physicists’ increased understanding of electricity and magnetism was the recognition that atoms are electrical in nature. In the 1830s Michael Faraday’s1 studies of the flow of electricity through solutions contributed evidence that electricity is itself “atomic,” i.e., made up of small indivisible units of electric charge. In 1894, G.J. Stoney proposed the word “electron” as the name for such a natural unit of charge. In 1897 the British physicist J.J. Thomson used electric and magnetic deflection to establish the existence of the tiny particle of electricity that we now call “the electron.” His work also showed that the electron is a fundamental component of every atom and intimately related to its chemical properties. By the end of the first decade of the twentieth century the American physicist Robert A. Millikan had measured the electron’s mass and charge to within one percent.
KeywordsInteger Multiple Inkjet Printer Elementary Charge Terminal Velocity Charged Droplet
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- 1.Michael Faraday, 1791–1867, born of a poor family near London, received only the equivalent of an elementary school education. Apprenticed to a bookbinder at thirteen, Faraday took to reading everything he could find, especially scientific books. Attendance at some lectures on chemistry by Sir Humphrey Davy led to his applying for and receiving a position as assistant to Davy. From this beginning, Faraday trained himself in science to the point where his discoveries in chemistry and electromagnetism, as well as his extremely popular public lectures, brought him renown and many honors.Google Scholar
- 2.Ordinary tap water has enough dissolved material to be a pretty good electrical conductor, which is why you should not stand in a puddle of water during alightning storm or become an electrolytic cell by touching a live wire.Google Scholar
- 3.See Great Experiments in Physics. Morris H. Shamos, Ed., Holt and Co., New York, 1959, p. 128, for extensively annotated excerpts from the original publications of Faraday on electrolysis and electromagnetism, as well as from the works of other important physicists. Short biographies of the pioneers we are discussing in this chapter are also included.Google Scholar
- 4.Opp. 254–255 in Experimental Researches in Electricity (3 vols. bound as 2) by Michael Faraday. Dover Publications, Inc., New York, 1965. The three volumes were originally published in 1839, 1844 and 1855 respectively.Google Scholar
- 5.Hertz’s experiment failed because of poor vacuum. He was working at the edge of what was technically possible in his time, and it was not good enough. Ionization of residual gas in his cathode-ray tube produced enough conductivity to short circuit the applied voltage and reduce the electric field to a value too low to produce any deflection.Google Scholar
- 6.Joseph J. Thomson, 1856–1940. See Shamos’s book, p. 216.Google Scholar
- 7.If you overdo this, you can cause the color alignment on the screen to go out of adjustment, and you will become quite unpopular with other users.Google Scholar
- 8.Robert A. Millikan, 1865–1953. See Shamos, op. cit., p. 238. The results of Millikan’s experiment are reported in Physical Review 32, 349 (1911).Google Scholar
- 9.R.A. Millikan, Electrons Press, Chicago, 1947, p. 75. (+ and –), Protons, Photons, Neutrons, Mesotrons and Cosmic Rays, revised edition, University of Chicago atoms interact with eachGoogle Scholar
- 10.Millikan claimed that his answer was precise to about a tenth of a percent. However, when other techniques became available to measure atomic spacings in solids to high precision, the value for Avogadro’s number derived from these data disagreed with the value calculated from Millikan’s e. The source of the discrepancy was ultimately traced to a slightly inaccurate value of the viscosity of air. Millikan used 18.240 µPa s; the currently accepted value is 18.324 µPa s. Scale Millikan’s value for e by the ratio of these two numbers and see what you get.Google Scholar
- 11.A quite detailed description of the considerations that went into the design of the inkjet printer developed by IBM for the IBM 46/40 Document Printer is given in “Application of Ink Jet Technology to a Word Processing Output Printer,” W.L. Buehner, J.D. Hill, T.H. Williams, and J.W. Woods, IBMJ. Res. Develop., 1–9 (Jan. 1977), and in other articles in this issue of the IBM Journal of Research and Development.Google Scholar
- 12.Search for fractional charges using droplet-jet techniques,” J. Van Polen, R. T. Hagstrom, and G. Hirsch, Phys. Rev. D36, 1983–89 (1987).Google Scholar