Lakeshore 336, User Manual

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Appendix A: Temperature Scales
A.1 Definition Temperature is a fundamental unit of measurement that describes the kinetic and
potential energies of the atoms and molecules of bodies. When the energies and
velocities of the molecules in a body are increased, the temperature is increased
whether the body is a solid, liquid, or gas. Thermometers are used to measure tem-
perature. The temperature scale is based on the temperature at which ice, liquid
water, and water vapor are all in equilibrium. This temperature is called the triple
point of water and is assigned the value 0 °C, 32 °F, and 273.15 K. These 3 tempera-
ture scales are defined as follows:
D
Celsius —abbreviation: °C. A temperature scale that registers the freezing point
of water as 0 °C and the boiling point as 100 °C under normal atmospheric pres-
sure. Formerly known as Centigrade. Originally devised by Anders Celsius (1701 -
1744), a Swedish astronomer.
D
Fahrenheit —abbreviation: °F. A temperature scale that registers the freezing
point of water as 32 °F and the boiling point as 212 °F under normal atmospheric
pressure. Originally devised by Gabriel Fahrenheit (1686 - 1736), a German phys-
icist residing in Holland; developed use of mercury in thermometry.
D
Kelvin —abbreviation: K. An absolute scale of temperature, the zero point of
which is approximately -273.15°C. Scale units are equal in magnitude to Celsius
degrees. Originally devised by Lord Kelvin, William Thompson, (1824 - 1907), a
British physicist, mathematician, and inventor.
A.2 Comparison The 3 temperature scales are graphically compared in FIGURE A-1.
A.3 Conversions To convert Fahrenheit to Celsius: subtract 32 from °F then divide by 1.8, or:
°C = (°F - 32) ÷ 1.8
To convert Celsius to Fahrenheit: multiply °C by 1.8 then add 32, or:
°F = (1.8 × °C) + 32
To convert Fahrenheit to kelvin, first convert °F to °C, then add 273.15.
To convert Celsius to kelvin, add 273.15.
FIGURE A-1 Comparison of kelvin, Celsius and Fahrenheit temperature scales
Boiling point of water
Freezing point of water
Absolute zero
kelvin
373.15 K
273.15 K
0 K
100 °C
0 °C
-273.15 °C
212 °F
32 °F
-459.67 °F
Celsius Fahrenheit