# PSV: Interconvert between different temperature scales

### Temperature

DEFINITION:

Temperature is a measure of the average kinetic energy of the molecules in a substance.

Measure temperature using physical properties of substance that change as a function of temperature:

• volume of a fluid (thermometer)
• resistance of a metal (resistance thermometer)
• voltage at the junction of two dissimilar metals (thermocouple)
• spectra of emitted radiation (pyrometer)

Temperature scales are defined in terms of these (and other) phenomena:

• freezing/boiling point of water
• resistance of a copper is X

Common temperature scales:

• Fahrenheit: Freezing point of water is 32 and boiling point is 212.
• Celcius: Freezing point of water is 0 and boiling point is 100.
• Rankine: Absolute zero (when all kinetic energy vanishes) is 0, increments = Fahrenheit. (459.67 R = 0 F)
• Kelvin: Absolute zero (when all kinetic energy vanishes) is 0, increments = Celcius. (273.15K = 0 C)

Converting temperatures:

• T(K) = T(C) + 273.15
• T(R) = T(F) + 459.67
• T(R) = 1.8*T(K)
• T(F) = 1.8*T(C) + 32

NOTE:

Converting temperature differences is slightly different (the additive corrections calcel out!).

OUTCOME:

Interconvert between different temperature scales

TEST YOURSELF!

Convert 20C to F. How about R? Convert -40C to F :)