Determine the gauge pressure given an absolute pressure of 2 atm and atmospheric pressure of 1 atm.
1 atm
Pressure can be reported on two different reference scales, and this question tests the relationship between them.
- Absolute pressure is measured from a perfect vacuum (true zero pressure), where there are no molecules exerting any force.
- Atmospheric pressure is the pressure of the surrounding air, taken here as 1 atm.
- Gauge pressure is measured relative to the local atmospheric pressure, because most pressure gauges read zero when open to the atmosphere.
The three are linked by:
Pabsolute = Patmospheric + Pgauge, so Pgauge = Pabsolute − Patmospheric.
Substituting the given values:
- Pgauge = 2 atm − 1 atm = 1 atm
This is why the answer is 1 atm. The value 2 atm is simply the absolute pressure copied unchanged — it ignores that the gauge is referenced to the atmosphere. The value 3 atm comes from mistakenly adding the two pressures instead of subtracting, which would give absolute-plus-atmospheric and has no physical meaning here. 0.5 atm corresponds to dividing rather than subtracting and is unrelated to the definition. A gauge reading of 1 atm here simply means the fluid is at twice atmospheric pressure in absolute terms.
Similar Questions
In fluid mechanics, zero absolute pressure corresponds to which condition?
Intensity of pressure at a point in a fluid is:
Why does the vapor pressure of a liquid increase with an increase in temperature?
Which of the following best defines the specific weight of a fluid?
Important Questions from Properties of Fluids
The Value of density of water is ________.
Specific Gravity of Mercury is ________.
The condition of "No-slip" at rigid boundaries is applicable to
One poise is equivalent to:
Dynamic viscosity has the dimensions as
