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There are three temperature scales in use today, Fahrenheit, Celsius and Kelvin.
Fahrenheit (F) temperature scale is a scale based on 32 for the freezing point of water and 212 for the boiling point of water, the interval between the two being divided into 180 parts; the 18th-century German physicist D. G. FAHRENHEIT originally took as the zero of his scale the temperature of an equal ice-salt mixture and selected the values of 30 and 90 for the freezing point of water and normal body temperature, respectively; these later were revised to 32 and 96, but the final scale required an adjustment to 98.6 for the latter value; until the 1970s the Fahrenheit temperature scale was in general common use in English-speaking countries; the Celsius, or centigrade, scale was employed in most other countries and for scientific purposes worldwide; since that time, however, most English-speaking countries have officially adopted the Celsius scale; the conversion formula for a temperature that is expressed on the Celsius (C) scale to its Fahrenheit (F) representation is: F = 9/5C + 32;
Celsius (C) temperature scale also called centigrade temperature scale, is the scale based on 0 for
the freezing point of water and 100 for the boiling point of water; invented in 1742 by the Swedish astronomer A. CELSIUS, it is sometimes called the centigrade scale because of the 100-degree interval between
the defined points; the following formula can be used to convert a temperature from its representation on the Fahrenheit ( F) scale to the Celsius (C) value: C = 5/9(F - 32); the Celsius scale is in general use
wherever metric units have become accepted, and it is used in scientific work everywhere;
Kelvin (K) temperature scale is the base unit of thermodynamic temperature measurement in the
International System (SI) of measurement; it is defined as 1/273.16 of the triple point (equilibrium among the solid, liquid, and gaseous phases) of pure water; the kelvin (symbol K without the degree sign) is
also the fundamental unit of the Kelvin scale, an absolute temperature scale named for the British physicist W. Thomson, Baron KELVIN;
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