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The two temperature scales normally
employed for measurement purposes are the Fahrenheit (F)and Celsius (C) scales. These
scales are based on a specification of the number of
incrementsbetween the
freezing point and boiling point of water at standard
atmospheric pressure. TheCelsius
scale has 100 units between these points, and the
Fahrenheit scale has 180 units. Thezero
points on the scales are arbitrary.The
freezing point of water was selected as the zero point of
the Celsius scale. The coldesttemperature
achievable with a mixture of ice and salt water was
selected as the zero point of theFahrenheit
scale. The temperature at which water boils was set at 100
on the Celsius scale and212
on the Fahrenheit scale. The relationship between the
scales is represented by the followingequations.
It is necessary to define an absolute
temperature scale having only positive values. The
absolutetemperature
scale that corresponds to the Celsius scale is called the
Kelvin (K) scale, and theabsolute
scale that corresponds to the Fahrenheit scale is called
the Rankine (R) scale. The zeropoints
on both absolute scales represent the same physical state.
This state is where there is no molecular motion of
individual atoms. The relationships between the absolute
and relativetemperature
scales are shown in the following equations.
The conversion of one temperature scale to
another is sometimes required at nuclear facilities,and the operator should be
acquainted with the process. The following two examples
will behelpful.
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