Liquid in glass thermometer diagram

The liquid in glass thermometer, is the most commonly used device to measure temperature and it is inexpensive to make and easy to use.

The liquid in glass thermometer has a glass bulb attached to a sealed glass tube (also called the stem or capillary tube).

A very thin opening, called a bore, exists from the bulb and extends down the centre of the tube.

The bulb is typically filled with either mercury or red-coloured alcohol and is free to expand and rise up into the tube when the temperature increases, and to contract and move down the tube when the temperature decreases.

In the Liquid In Glass Thermometers (LIG) the thermally sensitive element is a liquid contained in a graduated glass envelope.

The principle used to measure temperature is that of the apparent thermal expansion of the liquid.

A typical liquid-in-glass thermometer is shown in the figure below.

The background of the glass tube is covered with white enamel and the front of the glass tube forms a magnifying glass that enlarges the liquid column and facilitates with reading the temperature.

In Below Figure

what is liquid in glass thermometer