# Know Why Atmospheric Pressure Varies

Science deals with essential concepts like force, mass, pressure, velocity, atmosphere, volume, speed, time, temperature, and many more. Some of these quantities are dependent on external factors, and some are inter-dependent quantities. In this article, let us discuss an important concept, pressure.

Have you ever noticed that while hammering a sharp nail, you use less pressure and while hammering a blunt nail, you need to apply greater pressure? This is because the area of the end of the sharp nail is comparatively lesser than the area of the end of a blunt nail. The force applied is perpendicular to the surface of objects per unit area. When force is applied to an object, pressure is created. Pressure is also described as the ratio of the force to the area. Let us learn the types of pressure. We shall also learn more about the atmospheric pressure and the reason why it differs from place to place.

## Pressure and its Types

Pressure is the force applied perpendicular to the surface of an object per unit area, over which that force is distributed. Pressure is denoted by the letter p or P. The SI unit of pressure is the pascal (Pa). Pressure is measured using the formula given below.

P=F/A

Where,

P = pressure, F = magnitude of the force, and A = surface area in contact.

We have four types of pressure, they are:

• Absolute pressure
• Gauge pressure
• Differential pressure
• Sealed pressure or Vacuum pressure

Absolute pressure: Pressure that is relative to the zero pressure in the empty, air-free space of the universe is known as absolute pressure. Absolute pressure sensors are used for measuring barometric pressure variations, seen due to changes in atmospheric pressure.

Gauge pressure: This pressure is also referred to as relative pressure. It is the difference between absolute pressure and atmospheric pressure. Gauge pressure can be positive as well as negative.

Differential pressure: It is measured as the pressure difference between any two given points. This type of pressure is measured with the help of differential pressure sensors.

Sealed pressure or Vacuum pressure: This type of pressure is measured with reference to a sealed chamber closed with atmospheric pressure.

After discussing the types of pressure, let us now learn about atmospheric pressure.

### What is Atmospheric Pressure?

It is a type of pressure that is measured using a specific device known as the barometer. It is also referred to as Barometric pressure. It is defined as the force per unit area applied by an atmospheric column. Atmospheric pressure varies with the environmental conditions. One place may experience high atmospheric pressure while other places may experience low atmospheric pressure. It is the indicator of weather conditions. If the layer of air is thinner, there is lower atmospheric pressure. It decreases as altitude increases. Hence, mountain climbers carry bottled oxygen as they trek the high peaks.

It is exhibited in several different systems of units: standard atmospheres, kilopascals, millimeters of mercury, dynes per square centimeter, millibars (MB), and pounds per square inch (psi).