MECHANICAL THEORY Thermal Engineering

What is Pressure, Absolute Pressure and Vaccum Pressure

Want to know what’s the difference between these three terms? Here below I am providing a basic difference between Pressure, Absolute Pressure, and Vaccum Pressure in a detailed manner.


It is defined as the ratio of Force acting per unit Area of the cross-section.

Pressure (P)=F/A

SI Unit of Pressure is Here

Measurement of pressure is done by the manometer.

Absolute Pressure:

The Sum of Atmospheric pressure and Gauge pressure is called Absolute Pressure. or

The Difference between Atmospheric pressure and Vaccum pressure is also called as Absolute Pressure

Absolute Pressure=Atmospheric pressure+Gauge pressure

Absolute Pressure=Atmospheric pressure-Vaccum Pressure.

Vaccum Pressure:

It is defined as the difference between Atmospheric Pressure and the Absolute Pressure

 Vaccum Pressure = Atmospheric Pressure-Absolute Pressure.


Identify the signs of heat and work interaction in the following cases


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