Devices to measure pressure:
Devices to measure pressure Barometer – an instrument used to measure atmospheric pressure First used by Torrichelli 1 standard atmosphere (atm) = 760 mmHg
Slide 3:
Pressure Gauge – used to measure the pressure of a gas inside a container (bike tire, basketball, oxygen tank, etc.) Manometer – measures the pressure of a sample gas Open – compared to atmospheric pressure Closed – absolute measure
Atmospheric Pressure & Pressure Units:
Atmospheric Pressure & Pressure Units We live at the bottom of an ocean of air All the air above us presses down on us Standard unit is the Pascal (Pa), but it’s so small that we use the kilopascal (kPa) “ kilo- ” means 1000, so 1 kPa = 1000Pa 1 standard atmosphere (atm) = 101.3kPa
Other Pressure Units:
Other Pressure Units psi – Pounds per Square Inch Used on tires, etc. in Hg – Inches of Mercury Used by meteorologists, weather reports Equivalent Pressures 1 atm = 760 mmHg = 14.7 psi = 101.3 kPa = 29.92 inHg To convert:
Example:
Example Convert: 477 kPa = ___________ torr What would the pressure 26.5 psi be if it were expressed in units of in Hg ?