Explain the working of a clinical thermometer.

A clinical thermometer is a thermometer used to measure human body temperature. Mostly these thermometers are mercury-in-glass thermometers. They are accurate and sensitive, having a narrow place where the mercury level rises very fast. A kink in the tube stops the mercury level from falling on its own.

Most show both Celsius scale and Fahrenheit temperature scales, and run from 35 degree Celsius to 42 degree Celsius.

These are cleaned before and after each use, with alcohol.

A thermometer works on the principle that solids and liquids expand on heating. As the temperature rises, mercury expands causing it to move upwards and depict the temperature.

Medically, a maximum thermometer is often used, which indicates the maximum temperature reached even after it is removed from the body. As the temperature of the bulb rises, the liquid expands up the tube through the constriction or kink which prevents the mercury from falling back.