Magdeburg_hemispheres_small.png
Summary
Description Magdeburg hemispheres small.png |
English:
Drawing of a small pair of
Magdeburg hemispheres
from 1870s, used for demonstrating atmospheric pressure in natural philosophy classes. About 4-5 inches diameter. Magdeburg hemispheres were invented by
Otto von Guericke
in 1650. To use, the edges of the hemispheres were greased and pressed together, and a vacuum pump was attached to the port at bottom. When the air was evacuated from the inside, the valve at bottom was closed and the pump detached and the hemispheres would be held firmly together by atmospheric pressure. To demonstrate the pressure, ropes would be attached to the ring at top and a ring that could be screwed into the bottom (not shown), and audience members would be invited to try to pull the hemispheres apart. The force holding them together is equal to the area bounded by the circular joint between the hemispheres, multiplied by the difference between the inside and outside air pressure. For 5 inch hemispheres this would be about 280 lb. Alterations to image: removed figure number, increased brightness, and converted JPG to 32 color PNG.
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Date | |
Source | Retrieved 2008-06-27 from Adolphe Ganot & Edmund Atkinson (1872) Natural Philosophy for General Readers and Young Persons , D. Appleton & Co., New York, p.101, fig.90 on Google Books |
Author | Adolphe Ganot |
Permission
( Reusing this file ) |
Public domain in USA - first published in USA prior to 1923 |
Licensing
Public domain Public domain false false |
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publication
occurred prior to January 1, 1929, and if not then due to lack of notice or renewal. See
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