How is thermal expansion used in everyday life

Sometimes man's ingenuity has led him to find practical applications for these differences in thermal expansion between different materials. In other cases, he has developed technologies or applications that overcome the problems caused by the difference in thermal expansion between different materials. The thermally induced change in the length of a thin strip of metal differs for each material. For example, when heated, a strip of steel would expand by half as much as an equal length piece of aluminum.

Welding together a thin piece of each of these materials produces a bimetallic strip see Figure 1. The difference in expansion causes the bimetallic strip to bend when the temperature is changed. This movement has many common uses including: thermostats to control temperature, oven thermometers to measure temperature, and switches to regulate toasters. Some practical solutions to everyday thermal expansion problems in solids are: 1 The material developed for filling teeth has the same expansion as the natural enamel of the tooth.

Figure 2. Mercury and alcohol thermometers function because of the expansion difference between liquids and solids. Because the liquid expands at a different rate than the tube, it rises as the temperature increases and drops as the temperature decreases.

Courtesy of Gale Group. The manufacture of mercury and alcohol thermometers is based upon the expansion difference between solids and liquids see Figure 2. Thermometer fabrication consists of capturing a small amount of liquid mercury or alcohol inside an empty tube made of glass or clear plastic.

Because the liquid expands at a faster rate than the tube, it rises as the temperature increases and drops as the temperature decreases. The first step in producing a thermometer scale is to record the height of the liquid at two known temperatures i. A rivet is heated to red hot and passed through the plates. Then it is hammered to fix it firmly. On cooling, the rivet contracts and holds the plates together firmly. Bimetallic Strip and Thermostat Switches Bimetallic strips used in thermostats work on the principle of thermal expansion.

A bimetallic strip is a combination of two different metal strips, usually brass and iron, joined together with rivets. The two metals have different rates of thermal expansion.

Consider a bimetallic strip made of two metals A and B. Let the rate of thermal expansion of A be greater than that of B. When the bimetallic strip is heated, metal A expands more than metal B. As a result, the bimetallic strip bends, with metal A on the outer side of the bend. When the bimetallic strip is cooled, the metal-A contracts more than the metal-B. Then the bimetallic strip bends with the metal-B on its outer side. Working of A Thermostat Switch When a thermostat is used in an electrical circuit, its bimetallic strip gets heated and bends if the temperature in the circuit exceeds a certain limit.

Hence the circuit breaks. Since there is no current in the circuit now, the temperature of the strip decreases. The strip gets restored to its original position, and the circuit is completed, allowing current to flow again. Thermostats are used in appliances like geysers, refrigerators, electric irons, air conditioning machines, fire alarms, etc.

Expansion of Metal Pipes in Industries In certain industries, hot liquids or hot water is transported through metal pipes from one place to another. These pipes are subjected to expansion and contraction. To avoid cracks in the pipes when they expand and contract, they are arranged in the form of loops.

Thermometers A thermometer also works on the principle of expansion and contraction of matter on heating and cooling. Depending on the type of material used in thermometers, they are classified into solid, liquid and gas thermometers.

One of these metals expands more for each degree temperature rise than that other. This causes the bimetallic strip to curve as it is heated. This movement can act as an electrical switch by connecting a circuit, for example to turn on a fan, if the room temperature gets too hot. Other examples of thermal expansion include: - The air in a car tyre gets warm after a long journey and this increases its pressure.

Course overview. Here are five examples: 1 If you have ever tried to unscrew a stuck lid off a glass jar , you'll appreciate this expansion effect. This website uses cookies to improve your experience. We'll assume you're ok with this, but you can opt-out if you wish. Accept Read More. Close Privacy Overview This website uses cookies to improve your experience while you navigate through the website. Out of these, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website.