Robert Millikan

1. Robert Millikan By: Autumn,Rhett,Julian,Darien

2. …and his contributions to the Atomic Structure Theory…

3. In 1908, Millikan worked on an oil-drop experiment in which he measured the charge on a single electron .His experiment measured the force on tiny charged drops of oil suspended against gravity between two metal electrodes. If he knew the electric field, the charge on the droplets could be determined. He repeated the experiment for many oil drops. Millikan showed that the results could be explained as integer multiples of a common value (1.592 × 10−19coulomb), the charge on a single electron. This is a bit lower than the modern value of 1.602 176 53(14) x 10−19 coulomb because of Millikan's use of an inaccurate value for the viscosity of air.

4. How did the Oil-Drop Experiment Work? Millikan’s and Fletcher's apparatus incorporated a parallel pair of horizontal metal plates. By applying a potential difference across the plates, a uniform electric field was created in the space between them. A ring of insulating material was used to hold the plates apart. Four holes were cut into the ring, three for illumination by a bright light, and another to allow viewing through a microscope. A fine mist of oil droplets was sprayed into a chamber above the plates. Ordinary oil would evaporate under the heat of the light source causing the mass of the oil drop to change over the course of the experiment. Some oil drops became electrically charged through friction with the nozzle as they were sprayed. Alternatively, charging could be brought about by including an ionising radiation source (such as an X-ray tube). The droplets entered the space between the plates and, because they were charged, it could be made to rise and fall by changing the voltage across the plates.

5. Sourceswikipedia.org/wiki/Robert_Andrews_Millikan#Charge_of_the_electron&wikipedia.org/wiki/Oil-drop_experimentSourceswikipedia.org/wiki/Robert_Andrews_Millikan#Charge_of_the_electron&wikipedia.org/wiki/Oil-drop_experiment