Draw a well labelled diagram of a clinical thermometer.

Mercury is the only metal that is in liquid state at room temperature. It is used in thermometers because it has a high coefficient of expansion which makes it easy to move in the thermometers as per the temperatures. Mercury has a boiling point which makes it suitable to measure higher temperatures.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. ... As the temperature of the bulb rises, the liquid expands up the tube through the constriction.

Rectal thermometers, which go into your rear end, are the most accurate, but they can be uncomfortable. Armpit, ear, and forehead thermometers aren't as accurate. Most doctors think an oral thermometer, which you hold under your tongue, is best. A thermometer for measuring body temperature that has a constriction in the tube above the bulb preventing movement of the column of liquid downward once it has reached its maximum temperature so that it continues to indicate the maximum temperature until the liquid is shaken back down into the bulb.

A medical thermometer (also called clinical thermometer) is used for measuring human or animal body temperature.