hlwo aspirant

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in very simple we can say the pressure created by atmosphere is called atmospheric pressure.

or

atmospheric pressure is the pressure within the atmosphere of Earth. The standard atmosphere is a unit of pressure defined as 101,325 Pa, which is equivalent to 1013.25 millibars, 760 mm Hg, 29.9212 inches Hg, or 14.696 psi.

for example

When bulb is pressed, air present in tube and bulb escapes in the form of bubbles. However, there is atmospheric pressure on surface of liquid. When we release the bulb, the water moves inside the tube

hope this is helpful for you

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