Temperature scales

A temperature scale is defined with reference to a change in some a physical property. The resistance of a wire, the pressure of an enclosed mass of gas, the volume of an enclosed mass of mercury in a glass vessel etc. Each of these scales in the same at two fixed points, but may be different at some intermediate point.

Two fixed points are selected - for instance the lower value can be defined in terms of the melting point of ice at STP. The upper value can be defined as the boiling point of water, again at STP. The two fixed points are given values on a scale: zero and 100° on the Celsius scale.

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