Millikan+Experiment

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//From physick.wikispaces.com (Brandon Miller)//
 The oil drop experiment was an experiment performed by Robert Milikan and his assistant Harvey Fletcher in 1909 to  measure the elementary charge , or formerly know as the charge of a single electron. The experiment included balancing the  gravitational force down and and electric field  on tiny charged droplets of oil suspended between two metal plates. Since the density of the oil was known, the droplets' masses, and therefore their gravitational force could be determined from their radii. By repeating the experiment for many droplets, they confirmed that the charges were all increments of some fundamental value, and calculated it to be 1.60×10−19 C  which appears on the back of your formula sheet under elementary charge. (coulombs) By combining the force of electricity (Fe) and force of gravity (Fg) he came up with an equation to calculate the charge. Fe=Fg  q|E|=mg -> q=mg/|E|

Motivation for the experiment was that JJ Thompson discovered proof of the electrons existence using a Cathode Ray Tube (CRT) but had means of finding out the charge on the particle.

[[image:images-1.jpeg align="left"]]__**Robert Milikan(1868-1953)**__
Won the Nobel Prize in Physics for the experiment(1923) Professor at Chicago University (1910) Also recognized for his work confirming Einstein's photo electric effect experiment and obtaining the exact value for Planks constant.



__**Controversy **__
Of course with such an excellent advance in physics brings some controversy and allegations. Millikan made a deal with with his partner Fletcher that he himself could claim full credit of the results instead of sharing it.Fletcher then could take credit for another experiment even though this one won a Nobel Prize, Fletcher kept this information to himself until the day he died.There is some controversy over the use of selectivity in Millikan's results of his second experiment measuring the electron charge raised by the historian Gerald Holton. Holton (1978) pointed out that Millikan disregarded a large set of the oil drops gained in his experiments without apparent reason. Allan Franklin, a former high energy experimentalist has tried to rebut this point by Holton. Franklin contends that Millikan's exclusions of data did not affect the final value of //e// that Millikan obtained but concedes that there was substantial altering to fit his data that Millikan performed which had the effect of reducing the statistical value on //e//. This enabled Millikan to quote the figure that he had calculated //e// to better than one half of one percent; in fact, if Millikan had included all of the data he threw out, it would have been to within 2%

References: http://en.wikipedia.org/wiki/Oil_drop_experiment ldindustries.ca/LDIndustries/P30/LangdalePhysics30.html