what is atmospheric pressure? how is it caused
Answers
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Atmospheric Pressure:
Our atmosphere is made of different types of gases. Since gases exert pressure, thus Pressure exerted by air (present in atmosphere) is called atmospheric pressure.
We can define atmospheric pressure as the force per unit area exerted by the weight of the air.
Air pressure decreases as we move towards high altitudes.
Examples:-
- Astronauts wear special suit while going to space. This is because; in space there is no atmosphere.
- Ink pen starts leaking at higher altitudes as pressure inside the pen turns out to be much greater than air pressure at a hill station.
- Blood oozes out of the body as the blood in blood vessels flows with some pressure, so when blood vessels get injured, blood oozes out of our body.
Measuring Atmospheric Pressure :-
Atmospheric pressure can be measured by Barometer.
The simple barometer was constructed by Evangelista Torricelli.
It consists of a narrow, thick glass tube, about one meter long and sealed at the end.
The basic principle of the barometer is to use atmospheric pressure to balance vertical column of mercury sealed at the top.
A simple barometer consists of a long glass tube (closed at one end, open at the other) filled with mercury and turned upside down into a container of mercury.
As air pressure decreases, more of the mercury drains from the tube upto certain level and remains steady at particular height.
It does not fall as atmospheric pressure balances the mercury column in the tube at that level creating a vacuum above the mercury column. This vacuum space is called Torricellian vacuum.
The height of the mercury in the tube indicates the atmospheric pressure at that point of time.
At sea level, the height of the mercury in the barometer is found to be 76cm. this is known as 1 atmosphere (atm). The pressure equivalent to the 76cm column of mercury is approximately.
1 atm = 1.013 × 10⁵ Pa or N/ m²