Is a perfect vacuum measured as 0 psig?

Is a perfect vacuum measured as 0 psig?

• A. True
• B. False
• C. Depends on the context
• D. Not sure

Answer: (B)

A perfect vacuum is defined as the absence of matter and atmospheric pressure, which is measured as 0 psi (pounds per square inch) absolute (psia). However, when discussing pressure in the context of gauges specifically, the measurement is in psig (pounds per square inch gauge), which shows pressure relative to atmospheric pressure. In this context, a perfect vacuum corresponds to a measurement of -14.7 psig at sea level, since gauge pressure does not account for atmospheric pressure, which exerts a downward force. Thus, when the question specifies "0 psig," it implies that there is no pressure above atmospheric levels. In reality, a perfect vacuum cannot be achieved with a gauge pressure of 0 psig; it reflects atmospheric pressure at sea level. Therefore, the assertion that a perfect vacuum is measured as 0 psig is not correct, making the answer to the question false.

A perfect vacuum is defined as the absence of matter and atmospheric pressure, which is measured as 0 psi (pounds per square inch) absolute (psia). However, when discussing pressure in the context of gauges specifically, the measurement is in psig (pounds per square inch gauge), which shows pressure relative to atmospheric pressure. In this context, a perfect vacuum corresponds to a measurement of -14.7 psig at sea level, since gauge pressure does not account for atmospheric pressure, which exerts a downward force.

Thus, when the question specifies "0 psig," it implies that there is no pressure above atmospheric levels. In reality, a perfect vacuum cannot be achieved with a gauge pressure of 0 psig; it reflects atmospheric pressure at sea level. Therefore, the assertion that a perfect vacuum is measured as 0 psig is not correct, making the answer to the question false.