The charge carried by an electron is a fundamental constant of nature. R.A. Millikan, in 1909, was the first to show that this quantity was discrete and single valued. For this work, ant that on the photoelectric effect, he was awarded the Nobel Prize in 1923. In this adaptation of his experimental technique one can:
1. demonstrate the quantization of the charge on an electron,
2. determine the value of the elementary charge by the balancing field method, and
3. show that terminal velocity of a sphere is proportional to driving force (Stoke's Law).
The apparatus consists of (1) a viewing chamber, microscope, and illuminator for examining the movement of charged particles; (2) capacitor plates (part of the viewing chamber), switch, and binding posts for controlling the forces on the charged particles; and (3) a sphere injector for inserting particles into the chamber. The entire apparatus can be mounted on a support rod by means of a bottom hole and clamping screw; this allows the height to be adjusted to the observeršs eye level. Unlike Millikan who used oil drops, this experiment will be using small plastic spheres of known size and density. A bottle of plastic spheres suspended in solution is also included.