Compton generator: Difference between revisions
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{{short description|Physics apparatus to demonstrate rotation of Earth}} |
{{short description|Physics apparatus to demonstrate rotation of Earth}} |
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[[File:Watching the Earth revolve, Fig-4.jpg|thumb|Arthur Compton was experimenting by the Compton Generator.]] |
[[File:Watching the Earth revolve, Fig-4.jpg|thumb|Arthur Compton was experimenting by the Compton Generator.]] |
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A '''Compton generator'''{{sfn|Analytical Mechanics|p=280}}{{sfn|Classical Mechanics|p=365}} or '''Compton tube'''{{sfn|Blackie's Dictionary of Physics|p=72}} is an apparatus for experiment to demonstrate the [[Earth's rotation]], similar to the [[Foucault pendulum]] and to [[gyroscope]] devices{{sfn|A laboratory method of demonstrating the Earth's rotation|1913|p=803}} |
A '''Compton generator'''{{sfn|Analytical Mechanics|p=280}}{{sfn|Classical Mechanics|p=365}} or '''Compton tube'''{{sfn|Blackie's Dictionary of Physics|p=72}} is an apparatus for experiment to demonstrate the [[Earth's rotation]], similar to the [[Foucault pendulum]] and to [[gyroscope]] devices.{{sfn|A laboratory method of demonstrating the Earth's rotation|1913|p=803}} |
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== Explanation of apparatus == |
== Explanation of apparatus == |
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[[File:A Determination of Latitude, Fig1.jpg|thumb|Constraction of Compton generator.]] |
[[File:A Determination of Latitude, Fig1.jpg|thumb|Constraction of Compton generator.]] |
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A Compton generator is a circular hollow glass ring tube shaped like a doughnut |
A Compton generator is a circular hollow glass ring tube shaped like a doughnut, the inside of which is filled with water.{{sfn|Analytical Mechanics|p=280}} If the ring lies flat on the table, the water in the ring is stationary, and it is then turned over by rotating itself 180 degree around a diameter, such that it again lies flat on the table surface, which is horizontal. The result of the experiment is that the water moves with a certain constant drift velocity around the tube after the doughnut has been rotated. If there were no friction with the walls, the water would continue to circulate indefinitely.{{sfn|Analytical Mechanics|p=280}} |
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The ring used was made of one inch brass tubing bent into a circle eighteen inches in diameter |
The ring used in the initial experiment was made of one inch brass tubing bent into a circle eighteen inches in diameter, where the windows were placed the tube was constricted to a diameter of about three eights of an inch.{{sfn|A determination of latitude, Azimuth, and the length of the day independent of astronomical observations|1915|p=110&111}} |
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Compton used small droplets of coal oil mixed in the water to measure the drift velocity under a microscope{{sfn|Analytical Mechanics|p=281}} |
Compton used small droplets of coal oil mixed in the water to measure the drift velocity under a microscope.{{sfn|Analytical Mechanics|p=281}} |
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The experiment consists of laying the tube flat on a table until the water in it came to equilibrium, then slowly (in about 3 seconds) rotating it about an east-west axis until it had turned 180° and wasagain lyingflat on the table{{sfn|Analytical Mechanics|p=281}}. |
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== Analysis == |
== Analysis == |
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Assume the diameter of the glass tube is much smaller than the diameter of the ring, and <math>R</math> is the radius of the ring, <math>\omega</math> is the Earth rotation rate and <math>\lambda</math> is the latitude. |
Assume the diameter of the glass tube is much smaller than the diameter of the ring, and <math>R</math> is the radius of the ring, <math>\omega</math> is the Earth rotation rate and <math>\lambda</math> is the latitude. |
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Initially the ring is horizontal and the water is stationary. Second the ring is then quickly rotated by 180° around its East-West diameter and stopped, such that it again lies flat on the table surface, which is horizontal. At this time, the velocity <math>v_{th}</math> of the water in the tube is given by |
Initially the ring is horizontal and the water is stationary. Second the ring is then quickly rotated by 180° around its East-West diameter and stopped, such that it again lies flat on the table surface, which is horizontal. At this time, the velocity <math>v_{th}</math> of the water in the tube is given by |
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{{indent|4}}<math>v_{th} = 2 \omega R \sin \lambda</math> |
{{indent|4}}<math>v_{th} = 2 \omega R \sin \lambda</math> |
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Note that a rotation from the vertical to the vertical position produces the velocity <math>v_{tv}</math> of the water in the tube is given by |
Note that a rotation from the vertical to the vertical position produces the velocity <math>v_{tv}</math> of the water in the tube is given by |
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{{indent|4}}<math>v_{tv} = 2 \omega R \cos \lambda</math> |
{{indent|4}}<math>v_{tv} = 2 \omega R \cos \lambda</math> |
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== Experimental verification == |
== Experimental verification == |
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Compton used this measured drift velocity to |
Compton used this measured drift velocity to determine his latitude to within 3% accuracy.{{sfn|Analytical Mechanics|p=281}} |
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== References == |
== References == |
Revision as of 19:01, 14 September 2019
![](http://upload.wikimedia.org/wikipedia/commons/thumb/7/74/Watching_the_Earth_revolve%2C_Fig-4.jpg/220px-Watching_the_Earth_revolve%2C_Fig-4.jpg)
A Compton generator[1][2] or Compton tube[3] is an apparatus for experiment to demonstrate the Earth's rotation, similar to the Foucault pendulum and to gyroscope devices.[4]
Explanation of apparatus
![](http://upload.wikimedia.org/wikipedia/commons/thumb/0/0c/A_Determination_of_Latitude%2C_Fig1.jpg/220px-A_Determination_of_Latitude%2C_Fig1.jpg)
A Compton generator is a circular hollow glass ring tube shaped like a doughnut, the inside of which is filled with water.[1] If the ring lies flat on the table, the water in the ring is stationary, and it is then turned over by rotating itself 180 degree around a diameter, such that it again lies flat on the table surface, which is horizontal. The result of the experiment is that the water moves with a certain constant drift velocity around the tube after the doughnut has been rotated. If there were no friction with the walls, the water would continue to circulate indefinitely.[1]
The ring used in the initial experiment was made of one inch brass tubing bent into a circle eighteen inches in diameter, where the windows were placed the tube was constricted to a diameter of about three eights of an inch.[5]
Compton used small droplets of coal oil mixed in the water to measure the drift velocity under a microscope.[6]
Analysis
Assume the diameter of the glass tube is much smaller than the diameter of the ring, and is the radius of the ring, is the Earth rotation rate and is the latitude.
Initially the ring is horizontal and the water is stationary. Second the ring is then quickly rotated by 180° around its East-West diameter and stopped, such that it again lies flat on the table surface, which is horizontal. At this time, the velocity of the water in the tube is given by
Note that a rotation from the vertical to the vertical position produces the velocity of the water in the tube is given by
Experimental verification
Compton used this measured drift velocity to determine his latitude to within 3% accuracy.[6]
References
- ^ a b c Analytical Mechanics, p. 280.
- ^ Classical Mechanics, p. 365.
- ^ Blackie's Dictionary of Physics, p. 72.
- ^ A laboratory method of demonstrating the Earth's rotation 1913, p. 803.
- ^ A determination of latitude, Azimuth, and the length of the day independent of astronomical observations 1915, p. 110&111.
- ^ a b Analytical Mechanics, p. 281.
Bibliography
Journal
- Compton, Arthur Holly (1913). "A laboratory method of demonstrating the Earth's rotation". Science. 37: 803–806.
- Compton, Arthur Holly (1915). "A determination of latitude, Azimuth, and the length of the day independent of astronomical observations". Physical Review. 5 (2): 109–117.
- Compton, Arthur Holly (1915). "Watching the Earth revolve". Scientific American Supplement. 79: 196–197.
Books
- Hand, Louis N. (1999). Analytical Mechanics. Cambridge University Press. ISBN 978-0521575720.
- Taylor, John R. Classical Mechanics. S.Chand & Company Ltd. ISBN 978-1891389221.
- Blackie's Dictionary of Physics. S.Chand & Company Ltd. 2000. ISBN 978-8121942379.
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