What is Vacuum?

Most people think a vacuum is a place where there is absolutely no matter a place that contains absolutely nothing. According to scientist, however , such a thing is impossible. They believe there can be no region where there is not a single bit of any substance, not a molecule  of gas or the tiniest particle of dust. So a vacuum is actually a region where there is very little matter.

A good vacuum means an almost total lack of air, dust, and other samples of matter. But the key words "almost". One of the simplest ways to develop a a vacuum is to pump the air out of the container in which the vacuums are used in many important ways in industry. For examples, the electric bulb is worked on by a vacuum pump when it is being manufactured.

If air were to remain in the bulb, the oxygen in the air would cause the filament to burn up in a fraction of a second. In most modern bulbs, almost all the air is removed by pump. The same is true of the vacuum valves in radio or television sets. Just before they are sealed, as much air as possible is removed.

Probably one of the most familiar uses of a vacuum is the vacuum flask in lunch boxes. There is a double wall inside and a vacuum is produced between the two walls. Since there are very few molecules in a vacuum and they are far apart, the conduction of heat is prevented. This keeps the cold milk in a vacuum flask cold. And if a hot liquid is put in the flask, conduction of heat does not take place and the liquid stays hot.

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