How is gauge pressure defined?

• A. Pressure equal to atmospheric pressure
• B. Pressure below atmospheric pressure
• C. Pressure measured above atmospheric pressure
• D. Pressure at absolute zero

Answer: (C)

Gauge pressure is defined as the pressure measured above atmospheric pressure. This means that when gauge pressure is reported, it excludes the atmospheric pressure that is exerted on the measuring device. As a result, gauge pressure is useful for applications where one needs to know the pressure relative to the environment rather than the absolute pressure.

In practical terms, if a gauge reads zero at atmospheric pressure, then any reading above zero indicates how much pressure is being exerted above that atmospheric level. This is particularly important in various fields such as HVAC, automotive, and industrial processes where understanding the pressure exerted above the atmospheric level is critical for system efficiency and functionality.

To clarify the other options, atmospheric pressure is not inherently equal to any measured gauge pressure, it serves as a baseline. Pressure below atmospheric pressure refers to a vacuum, which is not applicable to gauge pressure. Lastly, pressure at absolute zero refers to a theoretical point of zero pressure, which is not relevant to the definition of gauge pressure.