Is 10 PSIG a greater pressure than 10 PSIA?

To understand the relationship between PSIG (pounds per square inch gauge) and PSIA (pounds per square inch absolute), it is essential to recognize what each term represents. PSIG measures pressure relative to atmospheric pressure, while PSIA measures pressure relative to a complete vacuum. Atmospheric pressure at sea level is approximately 14.7 PSI, which acts as the baseline for PSIG measurements.

When comparing 10 PSIG and 10 PSIA, it's important to convert the PSIG value into absolute pressure for accurate comparison. Since gauge pressure indicates pressure above atmospheric pressure, to find the absolute pressure equivalent of 10 PSIG, you would add atmospheric pressure (14.7 PSI):

10 PSIG + 14.7 PSI (atmospheric pressure) = 24.7 PSIA.

Thus, 10 PSIG is equivalent to 24.7 PSIA, making it clear that 10 PSIG is indeed at a higher pressure than 10 PSIA by the difference:

24.7 PSIA - 10 PSIA = 14.7 PSI.

Therefore, the correct choice indicates the pressure difference accurately as "by 14.7 PSI."