š Key Concepts
ā¢ Gauge vs absolute pressure on the chart (Inches Mercury Gauge vs Inches Mercury Absolute / Torr / Micron).
ā¢ How the chart shows that a deeper vacuum = lower absolute pressure (Torr, mm Hg, or microns).
ā¢ Unit relationships: 1 inch Hg ā 25.4 mm Hg, and 1 mm Hg = 1000 microns.
š Think About
ā¢ On the chart, which column(s) should you use to fairly compare all four choices, since some are in inches, some in mm, and some in microns?
ā¢ After converting everything to the same type of value (for example, mm Hg absolute), which option gives the smallest absolute pressure, and therefore the deepest vacuum?
ā¢ Where on the chart (top or bottom) do you find the deeper vacuums, and which of the listed values appears closest to that region when converted?:
ā
Before You Answer
ā¢ Be sure you are comparing absolute pressures, not gauge readings, when judging vacuum depth.
ā¢ Convert or read off each choice so they are all in the same unit (all in mm Hg abs or all in microns).
ā¢ Verify from the chart that the deepest vacuum corresponds to the highest % vacuum / lowest Torr or micron value, then see which choice matches that.