alleryStart learning →Gauge pressure is quoted relative to a chosen reference. Which reference does a pressure gauge use?
AA perfect vacuum inside the gauge
BThe pressure of the fluid at rest
CThe pressure at the ocean surface
DThe surrounding atmospheric pressure
Answer & Solution
Correct answer: D. The surrounding atmospheric pressure
1. A tyre gauge reads zero on a flat tyre even though atmospheric pressure is inside it.
2. That is because gauges are built to read zero at atmospheric pressure.
3. Gauge pressure is therefore the pressure measured relative to atmospheric pressure.
4. It is positive above atmospheric pressure and negative below it, so a perfect vacuum is not the reference.
_Source: OpenStax College Physics (CC BY 4.0), Ch 11 "Fluid Statics", section 11.6 Gauge Pressure, Absolute Pressure, and Pressure Measurement_
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