| 单词 | vacuum |
| 释义 | vacuum A space in which there is a low pressure of gas, i.e. relatively few atoms or molecules. A perfect vacuum would contain no atoms or molecules, but this is unobtainable as all the materials that surround such a space have a finite vapour pressure. In a soft vacuum (or low vacuum ) the pressure is reduced to about 10-2 pascal, whereas a hard vacuum (or high vacuum ) has a pressure of 10-2–10-7 pascal. Below 10-7 pascal is known as an ultrahigh vacuum . See also vacuum pump |
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