Most people think a vacuum is a place where there is absolutely no matter, a place that contains absolutely nothing, According to scientists, 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 a gas or the tiniest particle of dust. So a vacuum is actually a region where there is very little matter. A good vacuum moans an almost total lack of air, dust, and other samples of matter. But the keyword is “almost”.
One of the simplest ways to develop a vacuum is to pump the air out of the container in which the vacuum is to be formed. Very efficient vacuum pumps which are able to create good vacuums are used in many important ways in industry. For example, 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 a pump. The same is true of the vacuum valves in radio or television sets. Just 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 pro- duced 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.
What Is Meant By Vaccum?
1. a space entirely devoid of matter. 2. an enclosed space from which matter, esp. air, has been partially removed so that the matter or gas remaining in the space exerts less pressure than the atmosphere (opposed to plenum).