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. The equation for gauge pressure is $P_{gauge} = P_{absolute} - P_{atm}$.
3. In fluid statics, gauge pressures are commonly used because they simplify calculations by subtracting out atmospheric pressure.
4. A tire gauge measures the gauge pressure of the air inside a tire, not the absolute pressure.
5. In many practical applications, such as measuring blood pressure or water depth, gauge pressure is more relevant than absolute pressure.

Review Questions

• What is the relationship between gauge pressure and absolute pressure?
• Why might gauge pressure be more useful than absolute pressure in certain applications?
• If a car tire has an absolute pressure of 250 kPa and the atmospheric pressure is 100 kPa, what is its gauge pressure?

Related terms

Absolute Pressure: The total pressure exerted on a system, including atmospheric and any additional applied pressures.

Atmospheric Pressure: The weight of the Earth's atmosphere pressing down on everything at sea level, approximately equal to 101.3 kPa.

Pressure Measurement: $$\text\{Techniques and devices used to measure forces exerted by gases or liquids per unit area.\}$$