The Concept of Pressure

Have you ever wondered why we can only cut with sharp objects or why we need special shoes to walk on snow or why you can’t hammer a nail without a sharp end into the wall, or why a single nail bursts the balloon, but a bed of balloons can’t do that? The concept of pressure holds the answers to all of these issues. It is the ratio of the applied force to the region across which the force is applied. 

This relation tells us that higher pressure means large force or smaller area, or both. That is why to cut something efficiently, we require higher pressure, and for higher pressure, we need a smaller area which the sharp end of tools provide and hence we get our work done. Similarly, to walk on snow, we need shoes with a wider sole area so that force could be distributed and hence we could walk forward without sinking in the snow. This is known as the concept of pressure, which helps us to do work efficiently.

Formula of pressure

P=F / A

[F is the force, A is the area on which force is applied.]

Units of pressure

The SI unit of pressure is pascal denoted as Pa, which is equal to 1 N/m2. Before this, it was known as newtons per metre square.

100 kPa is equal to 1 bar, which is also another unit of pressure.

0.1 Pa is equal to 1 barye, also denoted as Ba, which is a unit used in the CGS unit system.

There are many other units of pressure used in different fields of science to define a constant value of pressure.

Another equation for pressure is,

Types of pressure

These are some basic types of pressure.

Absolute pressure

The pressure of having no matter inside a space, or a perfect vacuum, is defined as absolute pressure. This absolute zero serves as the reference point for absolute pressure measurements. A high vacuum will be sealed beneath the sensing diaphragm in order to make an absolute pressure sensor. As a result, if you leave an absolute pressure transmitter’s process pressure connection open to the air, it will read the absolute barometric pressure.

Differential pressure

The pressure differential refers to the difference in pressure between two places. This is very important in the industry for day-to-day pressure measurement.

It also refers to the fluid force per unit, which is measured in pounds per square inch (PSI). It’s the unit that’s removed from a force per unit that’s greater. Proper pressure differential measurement enables professionals in numerous sectors in finding the exact blockage point or evaluating if reservoir fluids can cause backing in the wellbore, causing drilling operations to be hampered. The pressure in different points of a fluid line must be taken into account for operations to be safe. Pressure differential measurement is useful for a variety of operations, including flow and liquid level measurement, filter monitoring, and clog detection. A high differential pressure, for example, could indicate that the filter is clogged.

The filter must be changed after the maximum amount of pressure differential has been reached, preventing unlikely outcomes such as damage or corrosion.

Atmospheric pressure

The air surrounding you is dense, pushing against anything it comes into contact with. When measuring atmospheric pressure, a barometer is frequently employed. When the weight of the atmosphere changes, a mercury column in a glass tube rises or falls in a barometer. Meteorologists measure atmospheric pressure by the height to which mercury rises.

A unit of measurement equivalent to the average atmospheric pressure at sea level is an atmosphere also written as atm at 15 degrees Celsius. One atmosphere contains 1,013 millibars of mercury or 760 millimetres. As height rises, atmospheric pressure decreases. The amount of oxygen available to breathe decreases as the pressure decreases. Because the available oxygen and air pressure are so low at such high elevations, people can become ill and possibly die.

Gauge pressure

Gauge pressure, denoted by a ‘g’ after the pressure unit. The gauge pressure is expressed as a percentage of the air pressure outside. The output of a gauge pressure sensor is directly influenced by changes in air pressure caused by weather conditions or altitude. Positive pressure is defined as a gauge pressure that is higher than the ambient pressure. Negative or vacuum gauge pressure occurs when the measured pressure is lower than atmospheric pressure.

Factors affecting pressure

The force exerted and the area on which the force is applied are the two basic factors that influence pressure. We can vary the pressure delivered to an item or surface by changing the area while keeping the force constant, changing the force while keeping the area constant, or changing both area and force at the same time. Hydraulics and brake systems both use the concept of pressure. We can use the notion of pressure to stop a car going at a fast speed by merely hitting the brake pedal, or we can use it to lift a big object by providing little force. 

Conclusion

In this article, we read about the concept of pressure, formula of pressure, unit of pressure, types of pressure and factors affecting pressure. We also read about different types of pressure like Absolute pressure, Gauge pressure, Differential pressure, and Atmospheric pressure. We learned that greater the area, smaller the pressure and greater the force, greater the pressure. The force exerted and the area on which the force is applied are the two basic factors that influence pressure. We can vary the pressure delivered to an item or surface by changing the area while keeping the force constant, changing the force while keeping the area constant, or changing both area and force at the same time.