robert millikan
Published on Nov 24, 2015
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PRESENTATION OUTLINE
background
- Robert Andrews Millikan (1863-1953)
- An American experimental physicist
- Graduated from Oberlin in 1891
- PhD from Columbia in 1895
- Nobel Prize in 1923
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Theory of elementary electric charge
- A focus of his Nobel Prize-winning research
- Millikan defined the electric constant, "e"
- Value : 1.6 x 10 ^ -19 Coulumbs
- "e" is a fundamental physical constant
- Demonstrates the positive electric charge of a proton
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the discovery : the oil drop experiment
- Millikan used a metal oil droplet apparatus
- Measured the electric field in relation to the drops
- This experiment proved...
- 1. Size/velocity of drops coincided w/ electricity
- 2. Particles have a universal singular charge, "e"
A small drop of oil in an electric field would move at a rate that balanced the forces of gravity, viscosity (of traveling through the air), and electric force. The forces due to gravity and viscosity could be calculated based on the size and velocity of the oil drop, so electric force could be deduced. Since electric force, in turn, is the product of the electric charge and the known electric field, the electric charge of the oil drop could be accurately computed. By measuring the charges of many different oil drops, it can be seen that the charges are all integer multiples of a single small charge, namely e.
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