Physical Quantities and Measurement - Measurement of Temperature

Temperature is defined as the degree of hotness or coldness of an object.

The S.I. unit of temperature is Kelvin ($K$), but it is commonly measured in degree Celsius ($^\circ C$) and degree Fahrenheit ($^\circ F$).

A thermometer is a device used to measure temperature, working on the principle of thermal expansion of liquids.

Mercury and Alcohol are commonly used thermometric liquids because they expand uniformly with heat.

The Clinical Thermometer is used to measure human body temperature. It has a range from $35^\circ C$ to $42^\circ C$ (or $95^\circ F$ to $108^\circ F$) and contains a 'kink' or constriction to prevent the mercury level from falling immediately.

The Laboratory Thermometer is used for scientific purposes with a typical range from $-10^\circ C$ to $110^\circ C$. It does not have a kink.

The normal temperature of a healthy human body is $37^\circ C$ or $98.6^\circ F$.

The lower fixed point is the melting point of pure ice ($0^\circ C$ or $32^\circ F$), and the upper fixed point is the boiling point of pure water ($100^\circ C$ or $212^\circ F$).