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Magdeburg_hemispheres_small.png (245 × 431像素,文件大小:17 KB,MIME类型:image/png


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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.
日期
来源 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
作者 Adolphe Ganot
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(二次使用本文件)
Public domain in USA - first published in USA prior to 1923

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Public domain
Public domain
這一媒體文件在美國屬於公有領域。這可用於版權過期的美國作品,通常這些作品發表於1929年1月1日之前。查看這個頁面可以獲取到更多的解釋。

United States
United States
這一圖片在美國以外可以沒有處於公有領域,特別是對美國作品不適用較短期限法則的國家,如加拿大、中國大陸(不含香港及澳門)、德國、墨西哥和瑞士。作品的作者和發表時間是關鍵信息,並且必須提供。參見 維基百科:公有領域維基百科:版權信息以獲取更多細節。

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Magdeburg hemispheres

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当前2008年6月27日 (五) 17:222008年6月27日 (五) 17:22版本的缩略图245 × 431(17 KB)Chetvorno{{Information |Description={{en|1=Woodcut of a small pair of Wikipedia:Magdeburg hemispheres from 1879s, used for demonstrating atmospheric pressure in natural philosophy classes.}} |Source=Retrieved 2008-06-27 from [http://books.google.com/books?id=s

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