How Does A Thermometer Work?

There are two types of thermometer: a mercury/alcohol thermometer and a spring thermometer.
The mercury or alcohol is placed within a glass. Both these expand when the temperature rises and contracts as it cools. So within the thermometer, the mercury or alcohol is forced upwards when it is warm and then falls as it cools. The glass is marked with degrees of heat, so it is easy to read the temperature which has been reached.
A spring thermometer works by having a piece of metal which is coiled and fixed to a pointer. The metal is sensitive to heat, so as the temperature rises, the metal expands and moves the pointer to the temperature reached.
The spring thermometer is less widely used and is not as accurate. Digital thermometers now electronically read temperatures which replace both the traditional types of thermometers. These are much more accurate and used particularly within medical settings where accuracy is extremely important.

It relies on the positive coefficient of expansion of its working fluid with temperature. When the working fluid gets warmer, it expands. The thermometer is usually configured so that small changes in the volume of the working fluid will register against a calibrated scale.

A thermometer which is used medically has got mercury. Once the thermometer is placed on the body if the body is hot the mercury expands and it shows the temperature of the body.

When you look at a regular outside bulb thermometer, you'll see a thin red or silver line that grows longer when it is hotter. The line goes down in cold weather.

This liquid is sometimes colored alcohol but can also be a metallic liquid called mercury. Both mercury and alcohol grow bigger when heated and smaller when cooled. Inside the glass tube of a thermometer, the liquid has no place to go but up when the temperature is hot and down when the temperature is cold.

Numbers are placed alongside the glass tube that mark the temperature when the line is at that point.
Picture of Spring Thermometer.

The other type of common thermometer is a "spring" thermometer. A coiled piece of metal that is sensitive to heat is used. One end of the spring is attached to the pointer. As the air heats, the metal expands and the pointer moves higher. As the air cools, the metal contracts and the pointer moves lower. Typically, these type of car thermometers are less accurate than bulb or digital thermometers. More information www.tmart.com/Car-Thermometers/

It works with the force