APPLICATIONS OF THE CHARACTERISTICS OF EXPANSION (7 Grade)

APPLICATIONS OF

THE CHARACTERISTICS OF EXPANSION

In general, solids, liquids and gases will expand if they are heated. The characteristics of subtance expansion can cause problem in human life.

After learning about the characteristics of subtance expansion, we can prevent the loss that occured as a consequence of the characteristics.

Here are some of problem caused by expansion and how to prevent and overcome them.

1. Rail Track Assembly

The connection between two railway tracks is always given space to prevent the tracks bending while they expand. When the temperature is hot during daylight, the rail track bar made of iron will expand. The space provide sometimes is not enough for the iron expansion. Therefore, nowdays tracks are designed with pointed ends ans assembled to be linked to each other in order to avoid the track being broken due to expansion.

2.  Space In Bridge Construction

To provide space for expansion, a metal bridge should have a space at the end. To enable the metal to move while expanding, the end of the metal bridge is supported by wheels so that it can glide easily during the expansion procces.

3.  Phone And Electrical Wires Assembly

Phone and electrical wires are intentionally made loose in hot daylight. The purpsose is to avoid the wire breaking on acold day due to contraction.

4.  Opening The Bottle Stopper

A metal stopper is sometimes hard to open. In order to open the stopper more easily, pour hot water inti it (or plunge it into hot water). After being heated, the stopper will expand so that it can be open easily.  This happens due to the fact that metal expansion is greather than glass expansion.

5.  Iron Hoops Assembled On A Barrel

Iron hoops are assembled on a barrel  by heating the hoops before it is assembled. After being heated, the iron hoop expans, so the circular size of the hoop  becomes bigger than the barrel. When it cools down, the iron hoop contracts and it is assembled strongly around the barrel.

6.  Sheet-Metal Riveting

Riveting is connecting two pieces of sheet metal using a rivet.

The rivet is heated until it glows white, then the rivet is put into the holr on the sheet metal and then the end of the rivet is hammered evenly. When the rivet  cools down, it contracts and clings both pieces of the sheet metal strongly. Shhet metal riveting is used in daily life, for instance in the assembly of the hull of a ship and a bimetallic strip.

7.  Bimetallic Strip

A bimetallic strip comprises of two metal strips  which are riveted into one.  Invar and bronze are usually utilized in assembling bimetal. Bimetallic strips are very sensitive to temperature change. If a bimetallic strip is heated, it will bend in the direction of the metal which has a lower expansion coefficient; and if a bimetallic strip is cooled, it will bend toward the direction of the metal with the higher expansion coeffisient.

Bimetal is used on:

a.    Turn signals on cars and motorcycles

The turn signals (directional signals) will go on and off depending on the movement of the bimetal, whether it is connected or separated.

In turns, the metal movement in the bimetal causes a large electric barrier so that the lamp goes off, and causes a small elctrical resistance so that the lamps turns on.

b.    Thermostat bimetal

A thermostat is a device utilized to regulate temperature.

We can find a thermostat in, for example, an incubator, an electrical iron, a roomheater, a refrigenerator, and an electronical stove.

The work principals of a thermostat are given below.

1)    When the room temperature is warm, the bimetal strip will bend toward the dirrection of the iron, so that it will separate the contact and disconnect the electricity flow ti the heating element.

2)    When the room temperature is cold, the bimetal strip becomes straight again, so the contact is connected and the electricity flow is connected to the heating element again.

Therefore, a thermostat is used to turn off and turn on the heating element in a room. Its purpose is to regulate the room temperature to keep it steady in particular degrees only by turning the button according to our needs.