Unit of Pressure - Unit, Types, FAQs

Edited By Vishal kumar | Updated on Sep 24, 2024 04:10 PM IST

Pressure:

Pressure is defined as the force applied perpendicular to an object's surface per unit area across which that force is diffused.
P=F/A
Where, the pressure is P, the normal force is F, and the area of the surface on contact is A.
The pressure gauge in relation to the ambient pressure is known as gauge pressure. Pressure is measured in a variety of ways. Some of these are derived from a unit of force divided by a unit of area; for example, the SI unit of pressure, the pascal(Pa), is one newton per square metre(N/m2); similarly, the imperial and US customary systems' conventional unit of pressure is the pound-force per square inch (psi).

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Unit of Pressure - Unit, Types, FAQs

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The amount of force delivered at right angles to an object's surface per unit area is known as pressure. P is the symbol for it. The IUPAC recommends a lower-case p for pressure. Upper-case P, on the other hand, is extensively used. The use of P vs p is determined by the field in which one is employed, the presence of additional symbols denoting quantities such as power and momentum in the direct proximity, and writing style.

The quantity of pressure is a scalar quantity. It connects the normal force operating on the surface to the vector area element. The scalar proportionality constant that connects the two normal vectors is called pressure.

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Unit of pressure:

The unknown quantities are compared to a unit, which is a standard quantity. A specified magnitude of a physical quantity that has been adopted by law or convention is defined. For example, pascal (Pa) is the unit for pressure.

The pascal (Pa) is a SI unit or MKS unit for pressure, equivalent to one newton per square metre (N/m2, or kgms2). Pressure in SI was repeatedly expressed in newton per square metre. Other pressure units are frequently used, such as pounds per square inch (lbf/in2) and a bar.

The CGS unit of pressure is equal to 1 dyn.cm-2 or 0.1 Pa. However, with SI, using the term kilogram, gram, kilogram-force, or gram-force (or their symbols) as units of force is specifically prohibited.

The system which is a logical set of units based on the fundamental units of centimetre, gram, and second for distance, mass, and time is the CGS system. The MKS system, which was based on the fundamental units of metre for distance, kilogram for mass, and second for time, subsequently substituted it.

As a result, it is associated with energy density and can be expressed in joules per cubic metre. Pressure is a measure of potential energy conserved per unit volume because a system under pressure has the ability to work on its surroundings.

Atmospheric pressure:

The pressure within Earth's atmosphere, often known as atmospheric pressure or barometric pressure. The hydrostatic pressure induced by the weight of air above the measurement location roughly approximates atmospheric pressure. Because there is less overlaying atmospheric mass as height rises, atmospheric pressure falls as elevation rises.

The force exerted on the atmospheric gases above the surface by the planet's gravitational influence is a function of the planet's mass, the radius of the surface, the volume and composition of the gases, as well as their vertical distribution in the atmosphere.The planetary rotation, as well as local elements such as wind velocity, temperature-induced density variations, and composition changes, have an impact on it.

The force produced by the weight of the air molecules is referred to as air pressure. Even the tiniest air molecules have mass, and the huge amounts of air molecules that make up the layers of our atmosphere have a lot of mass together.

Temperature affects air pressure because as the air warms, the molecules begin to move around more, causing them to collide more frequently and create higher pressure. However, air pressure has an impact on temperature because the more those molecules collide, the more heat is generated. The application of atmospheric pressure is that, when a man sucks fluid from a straw, for example, the pressure within is moderately low, and the atmospheric pressure outside drives up the fluid into the straw. When a vacuum cleaner is powered on, the pressure inside plunges off due to air inside.

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Unit of atmospheric pressure:

The pascal (Pa) is the SI unit of pressure, which is defined as a force of one Newton per square metre. The calculation is as follows for converting between atm, Pa, and torr, 101325 Pa =760 torr=1 atm. It's sometimes referred to as a reference or standard pressure. It is almost equal to the atmospheric pressure at sea level on Earth.

Measurement of the pressure and the atmospheric pressure:

Pressure metres, pressure gauges, and vacuum gauges are instruments that measure and show pressure in an integral unit. A manometer is a good example, as it measures and indicates pressure by using the surface area and weight of a column of liquid. A barometer, typically known as barometric pressure, is a scientific device used to measure atmospheric pressure.

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Types of pressure:

Fluid pressure:

The compressive tension at a point within a fluid is commonly referred to as fluid pressure.

Fluid pressure can occur in one of two situations: open channel flow, such as in the atmosphere, or closed channel flow, such as in the ocean.

In most cases, pressure in open conditions can be approximated by pressure in "static" or non-moving conditions, since the motions cause relatively minor variations in pressure. Such circumstances are consistent with fluid statics principles. The hydrostatic pressure is the pressure in a non-moving (static) fluid at any given place. Closed bodies of fluid are either "static" or "dynamic," depending on whether the fluid may move, as in a pipe or by squeezing an air gap in a closed container. The pressure in closed situations is consistent with fluid dynamics principles.

Vapour pressure:

Vapour pressure is a measurement of a vapour in thermal equilibrium with its condensed phases in a closed environment.. All liquids and solids have a potential to evaporate into gas, and all vapours have a potential to condense back into their liquid or solid state. The temperature at which the vapour pressure equals the ambient air pressure is known as the normal boiling point of a liquid which is the boiling point of a liquid under atmospheric pressure. Partial vapour pressure is the surface tension that a single component in a mixture contributes to the ambient pressure in the system.

Liquid pressure:

Water pressure acts on a person's eardrums while he or she dives under the water. The stronger the pressure, the deeper the swimmer swims. The weight of the water above the individual is causing the pressure. As a swimmer swims deeper, there is more water above them, resulting in increased pressure. The pressure exerted by a liquid is proportional to its depth. The density of the liquid also affects liquid pressure. The pressure would be higher if someone was submerged in a liquid that was denser than water. As a result, we may state that depth, density, and liquid pressure are all proportional.

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NCERT Physics Notes:

Frequently Asked Questions (FAQs)

1. Define pressure and its formula.

Pressure is defined as the force applied perpendicular to an object's surface per unit area across which that force is diffused.

P=F/A

Where, the pressure is P, the normal force is F, and the area of the surface on contact is A.

2. What is the unit of pressure?

The pascal (Pa) is a SI unit or MKS unit for pressure, equivalent to one newton per square metre (N/m2, or kgms2).
The CGS unit of pressure is equal to 1 dyn.cm-2 or 0.1 Pa.

3. Define atmospheric pressure.

The pressure within Earth's atmosphere, often known as atmospheric pressure or barometric pressure. The gravitational attraction of the planet on the atmospheric gases above the surface causes atmospheric pressure.

4. What is the application of atmospheric pressure?

The applications of atmospheric pressure is that,

When a man sucks fluid from a straw, for example, the pressure within is moderately low, and the atmospheric pressure outside drives up the fluid into the straw.
When a vacuum cleaner is powered on, the pressure inside plunges off due to air inside.

5. What is the unit of the atmospheric pressure?

The pascal (Pa) is the SI unit of pressure, which is defined as a force of one Newton per square metre.
The calculation is as follows for converting between atm, Pa, and torr, 101325 Pa =760 torr=1 atm.
It's sometimes referred to as a reference or standard pressure.