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A convenient operational definition of '''temperature''' is that it is a measure of the average translational kinetic energy associated with the disordered microscopic motion of atoms and molecules.<ref> http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/temper.html </ref>  

A convenient operational definition of '''temperature''' is that it is a measure of the average translational kinetic energy associated with the disordered microscopic motion of atoms and molecules.<ref> http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/temper.html </ref>  

Temperature is expressed in degrees (symbol: ° ). There are two units of temperature in common use - [[Celsius degree|Celsius]] (°C) and [[Fahrenheit degree|Fahrenheit]] (°F). Both make reference to the freezing and boiling points of pure water at normal atmospheric pressure.   

Temperature is expressed in degrees. There are two units of temperature in common use - [[Celsius degree|Celsius]] (°C) and [[Fahrenheit degree|Fahrenheit]] (°F). Both make reference to the freezing and boiling points of pure water at normal atmospheric pressure.   

Celsius (sometimes known as centigrade) sets the freezing point at 0 degrees (°C) and the boiling point at 100 degrees (100°C).<br>

Celsius (sometimes known as centigrade in the past) sets the freezing point at 0 degrees (0 °C) and the boiling point at 100 degrees (100 °C).<br>

Fahrenheit sets the freezing point at 32 degrees (32°F) and the boiling point at 212 degrees (212°F).<br>

Fahrenheit sets the freezing point at 32 degrees (32 °F) and the boiling point at 212 degrees (212 °F).<br>

Conversion of Fahrenheit to Celsius:  °C = ( °F - 32 ) x 5 ÷ 9<br>

Conversion of Fahrenheit to Celsius:  °C = ( °F - 32 ) x 5 ÷ 9<br>

Conversion of Celsius to Fahrenheit:  °F = ( °C x 9 ÷ 5 ) + 32

Conversion of Celsius to Fahrenheit:  °F = ( °C x 9 ÷ 5 ) + 32

Universally Celsius is the predominant system but Fahrenheit still holds sway in the USA.

Universally Celsius is the predominant system but Fahrenheit still holds sway in the USA.

An alternative scale is used in scientific circles.  This is based on the value of a Celsius degree and is expressed as degrees [[Kelvin]] (°K) after the famous Irish-born physicist. The Kelvin scale sets 0° as the coldest possible temperature in the universe, where an object has no thermal energy, this is known as '''absolute zero''' and equates to -273.15°C or -459.67°F.

An alternative scale, the [[Kelvin]] scale (after the famous Irish-born physicist), is used in scientific and engineering circles. It is a [[thermodynamic (absolute) temperature]] scale: it sets 0 K at the '''absolute zero''': the coldest possible temperature in the universe, where an object has no thermal energy. The unit of the Kelvin scale (K) is equal to the unit of the Celsius scale (°C). Thus the freezing point of water at normal atmospheric pressure occurs at 273.15 K.

 

The Kelvin is one of the fundamental seven [[SI units]]. Today the [[Kelvin]] is defined by two points: the absolute zero and the [[triple point]] of water (273,16 K).

 

In US engineering fields another scale, the [[Rankine]] scale, is still used. As the Kelvin it is a thermodynamic (absolute) temperature scale, but one Rankine unit (°R) equals one Fahrenheit unit (°F). Thus, the freezing point of water at normal atmospheric pressure occurs at 459.67 °R.

==References==

==References==

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[[category:physics]]

[[category:physics]]