Torr

Definition

Torr is a unit of pressure measurement that is commonly used in the context of vacuum and gas pressure. It is named after the Italian scientist Evangelista Torricelli, who invented the barometer. The torr is defined as the pressure exerted by a column of mercury 1 millimeter high at the standard acceleration of gravity.

5 Must Know Facts For Your Next Test

1. One torr is equivalent to 1/760th of an atmosphere, or approximately 133.322 pascals (Pa).
2. Torr is commonly used to measure vacuum pressure, with typical values ranging from 760 torr (atmospheric pressure) down to 10^-9 torr (ultra-high vacuum).
3. Gauge pressure is often measured in torr, with positive values indicating pressure above atmospheric and negative values indicating pressure below atmospheric.
4. Absolute pressure is the sum of gauge pressure and atmospheric pressure, and can also be expressed in torr.
5. Pressure measurement devices, such as manometers and barometers, can be calibrated to display readings in torr.

Review Questions

• Explain how the torr unit is related to the measurement of gauge pressure.
  • Gauge pressure is the pressure measured relative to the surrounding atmospheric pressure, which is typically taken as the reference point. The torr unit is commonly used to express gauge pressure, with positive values indicating pressure above atmospheric and negative values indicating pressure below atmospheric. For example, a gauge pressure of 500 torr would indicate a pressure 500 torr above the standard atmospheric pressure of 760 torr.
• Describe the relationship between absolute pressure, gauge pressure, and the torr unit.
  • Absolute pressure is the total pressure acting on a surface, including both the gauge pressure and the atmospheric pressure. Absolute pressure can be expressed in torr, which is a unit of pressure measurement defined as the pressure exerted by a column of mercury 1 millimeter high at the standard acceleration of gravity. The relationship between absolute pressure, gauge pressure, and torr can be expressed as: Absolute Pressure (in torr) = Gauge Pressure (in torr) + Atmospheric Pressure (in torr).
• Analyze the significance of the torr unit in the context of pressure measurement and vacuum technology.
  • The torr unit is particularly useful in the context of vacuum and gas pressure measurement. Vacuum pressure is typically measured in torr, with values ranging from 760 torr (atmospheric pressure) down to 10^-9 torr (ultra-high vacuum). The ability to precisely measure and control pressure in the torr range is crucial for various applications, such as semiconductor manufacturing, particle accelerators, and scientific research. The torr unit allows for the accurate quantification of pressure, which is essential for maintaining the appropriate conditions in these specialized environments and ensuring the proper functioning of vacuum-based technologies.

Related terms

Absolute Pressure:

Absolute pressure is the total pressure acting on a surface, including both the gauge pressure and the atmospheric pressure.

Gauge Pressure:

Gauge pressure is the pressure measured relative to the surrounding atmospheric pressure, which is typically taken as the reference point.

Atmospheric Pressure:

Atmospheric pressure is the pressure exerted by the weight of the earth's atmosphere on the surface, typically measured in torr or millimeters of mercury (mmHg).