Air pressure, also known as atmospheric pressure, is the force exerted by the weight of the air above a given point on Earth’s surface. It is typically measured using the unit called “pascal” (Pa), which is the SI unit of pressure. One pascal is defined as one newton per square meter (N/m²). In addition to pascals, air pressure is also commonly measured in other units such as millibars (mb) or inches of mercury (inHg), depending on the application and region.
To measure air pressure, various instruments are used depending on the range and accuracy required. One common instrument is the mercury barometer, which consists of a vertical glass tube partially filled with mercury. The height of the mercury column in the tube changes in response to atmospheric pressure changes. Standard atmospheric pressure at sea level supports a column of mercury about 760 mm (29.92 inches) high. This height, known as standard atmospheric pressure, corresponds to approximately 1013.25 millibars or 101.325 kilopascals.
In classrooms or educational settings, students may use simpler devices like an aneroid barometer to understand atmospheric pressure concepts. An aneroid barometer uses a small, flexible metal box called an aneroid cell that expands or contracts with changes in air pressure. This movement is then displayed on a dial calibrated in units such as inches of mercury or millibars.
Measuring air pressure accurately is crucial for weather forecasting, aviation, and various industrial applications. Instruments like barometers provide real-time measurements that help meteorologists monitor weather patterns, pilots navigate aircraft safely, and engineers design systems that operate effectively under varying atmospheric conditions.