Gauge pressure

Definition

Gauge pressure is the pressure relative to atmospheric pressure. It is the difference between absolute pressure and atmospheric pressure.

5 Must Know Facts For Your Next Test

1. Gauge pressure can be positive or negative, depending on whether the measured pressure is above or below atmospheric pressure.
2. It is commonly used in various applications such as tire pressure measurements and blood pressure readings.
3. The relationship between gauge pressure ($P_g$), absolute pressure ($P_a$), and atmospheric pressure ($P_{atm}$) is given by $P_g = P_a - P_{atm}$.
4. When using a manometer, the height difference of the fluid columns directly correlates to the gauge pressure of the system being measured.
5. In fluid mechanics, gauge pressures are often more practical than absolute pressures for measuring and calculating forces in closed systems.

Review Questions

• What is the formula that relates gauge pressure, absolute pressure, and atmospheric pressure?
• Why might gauge pressure be more convenient to use than absolute pressure in practical situations?
• How can you determine gauge pressure using a manometer?

Related terms

Absolute Pressure: The total actual pressure at a point, including atmospheric pressure. It is always greater than or equal to zero.

Atmospheric Pressure: The force per unit area exerted against a surface by the weight of air above that surface in the atmosphere. Standard atmospheric pressure at sea level is approximately 101.3 kPa.

Manometer: An instrument used to measure the gauge pressures of a fluid by comparing it with an external reference, usually atmospheric pressure.