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Object Required
Study of atmospheric pressure measurement by using scientific instrumesnts. Such as Barometer and Manometer.
Principle
It works on the principle of torricelli. When a tube filled with murcury turnend down on a cistern filled with murcury then dur to atmospheric pressure mercury in tube goes in up ward direction
Theory
Barometer :- An instrument that is used to measure atmospheric pressure is called a barometer. The most common types are the mercury barometer and the aneroid barometer. A mercury barometer is made by inverting a mercury - filled tube in a container of mercury as shown in fig. 3.8 . The pressure at the top of the mercury barometer will be the vapor pressure of mercury. Thus , atmospheric pressure will push the mercury up the tube to a height h. The mercury barometer is analyzed by applying the hydrostatic equation. Thus by measuring h, local atmospheric pressure can be determined using. An aneroid barometer works mechanically. An aneroid is an elastic bellows that has been tightly sealed after some air was removed. When atmospheric pressure changes, this causes the aneroid to change size, and this mechanical change can be used to deflect a needle to indicate local atmospheric pressure on a scale.
Manometer :- A manometer , often shaped like the letter "U," is a device for measuring pressure by raising or lowering a column of liquid , for example , Fig, 3.11 shows a U - tube manometer that is being used to measure pressure in a flowing fluid . In the case shown, positive Gage pressure in the pipe pushes the manometer liquid up a height . To use a manometer engineers relate the height of the liquid in the manometer to pressure as illustrated in Example 3.6 . Once one is familiar with the basic principle of manometry , it is straightforward to write a single equation rather than separate equation as was done in Ex. 3.6 . The single equation for evaluation of the pressure in the pipe .One can read the equation in this way : zero pressure at the open end, plus the change in pressure from point 1 to 2 , minus the changes in pressure from point 3 to 4, equals the pressure in the pipe . The main concept to remember is that pressure increases as depth increases and decreases as depth decreases..
Conclusion
We can measure atmospheric pressure by using this equipment in shorter period of time by using liquid mercury . Which makes it comfortable and portable to use any where easily and in any environment and it is also less costly. But aneroid barometer is advantageous then mercury barometer because it is smaller in size and give the result less time. Because it works mechanically. Manometer is useful in following fluid pressure measurement . It also gives accurate result by measuring the height of mercury increased in tube at open side . This shows the pressure of fluid by adding atmospheric and vacuum pressure.
Published Date
30 May, 2018