The amount of force exerted on a surface per unit area is defined as ‘Pressure’. It can also be defined as the ratio of the force to the area (over which the force is acting).
Formula and Unit of Pressure
Pressure (P) = Thrust/ Area
The SI unit is ‘pascals (Pa)’. 1 Pa = 1N/m2
Example: It is easier to hammer a sharp pin than to hammer a blunt pin. This is because the area at the end of the sharp pin is smaller than the area at the end of a blunt pin. This leads to an increase in pressure leading to hammer the sharp pin easily.
Types of Pressure
- Atmospheric Pressure
- Absolute Pressure
- Differential Pressure
- Gauge Pressure
Atmospheric Pressure
The pressure exerted by the weight of the atmosphere, which at sea level has a mean value of 101,325 pascal (roughly 14.6959 pounds per square inch).
Absolute Pressure
The definition of absolute pressure is the pressure of having no matter inside a space, or a perfect vacuum. Measurements taken in absolute pressure use this absolute zero as their reference point. The best example of an absolute referenced pressure is the measurement of barometric pressure.
Differential Pressure
Differential pressure, in general, is a measure of pressure where the reading and reference values are variable.
Gauge Pressure
The amount by which the pressure measured in a fluid exceeds that of the atmosphere.
Primary Measuring Element of Pressure
Mechanical pressure-sensing elements include the bellows, the diaphragm, and the bourdon tube. Each of these devices converts a fluid pressure into a force. If unrestrained, the natural elastic properties of the element will produce a motion proportional to the applied pressure.
