Applications of Thermal Expansion

 

The knowledge of the principle of thermal expansion of solids have been helpful in construction of some buildings, bridges, railway lines, telephone wires, the bimetallic strip in electric iron, electric fire alarm and so on. Let's take a look at some of the applications of thermal expansion in solids:

• Expansion of glass

When hot water is poured into a glass container, it cracks. This is because the heat causes a rapid expansion on the inside of the glass container than on the outside, causing a strain on the glass. Therefore, in laboratories where glass instruments are used, pyrex is employed in the production of such instruments to avoid cracks.

Also, the tight stopper of a glass bottle can be removed by placing the glass bottle in a hot water, while the stopper does not touch the hot water. As the heat is applied on the bottle, it expands and so the stopper can then be easily removed from the bottle.

• Electric Fire Alarm

The electric fire alarm consists of a bimetallic strip (copper and iron) which gets heated up whenever there is a fire outbreak in a building. The heat causes the strip to bend, thus completing the circuit causing the ringing of the bell known as the fire alarm.

• Electric Iron

The bimetallic strip of an electric thermostat is used as a make-and-break device in an electric iron to regulate the temperature of the electric iron. The heat generated by the flow of electric current causes the bimetallic strip to bend away from the contact point, switching off the flow of electric current. When the strip cools, it straightens and makes contact again, thus switching on the electric current. This helps to control the temperature of the electric iron.

• Railway Tracks
  
  
  

To allow for free expansion and contraction of rail tracks, they are designed with gaps in-between the rails. On hot days, the rail tracks will not swell up nor buckle thus providing a safe path for trains.

• Construction of Bridges

To allow for expansion in bridges made of steel, one end of the steel girders is fixed while the other end rests on rollers creating an expansion gap. This is because if both ends are fixed and the girders expand, the bridge will bend.

• Building Roofs

The creaking noise often heard in the roof of buildings is a result of the expansion of the galvanized roofing sheets as they are heated by the hot sun.