EXPANSION

THE EXPANSION OF SOLID

l Length expansion happen’s in the long solid’s with small section area. For example, in the metal bar. To investigate the length expansion in solid’s we can use misschenbroek device.

l Length expansion coefficient is a number that shows the increase of length per 1 metre in temperature increase of 1 K or 1 ⁰C

l The length expansion coefficient is formulated as follows :

            1.         a   : length expansion cofficient

            2.         Δƪ : the change of length

            3.         Δt : the change of temperature

            4.         ƪ˳ : initial length

            5.         ƪι : final length of the body after it is heated

            6.         t˳ : initial temperature

            Δƪ {read : delta ƪ }

            Δι {read : delta ι}

AREA EXPANSION

n Area expansion can be investigated in solid which is flat or thin disk-shaped, for example window glass.

n Area expansion coefficient is symbolized ß {read : betha }and it is defined as the ratio between area increase to the initial area of body perthe unit of temperature increase

n The relationship of ß and a is  ß : 2 a

Expansion principle in everyday life

1.       The expansion principle of metter which beneficial in everyday life are as follow’s

2.       Thermometer

3.       Liquid expansion such as mercury and alcohol in thermometer tube is used as the indicator of  temperature

4.       Riveting Metal Plate

5.       Riveting is to connect two metal plates by using a riveting nail

6.       Bimetal plates

            Bimetalic plates are the combination of two metal plates with diferent expansion coefficient         

               riveted to be one.

•         Bimetal plates if they are heated, they will bend to the direction of the metal exapnsion coefficient of which is smaller.

•         Bimetal plates are many used in the following devices.

ü Thermal switch, that is a switch that work based on thermal expansion. The termal switch is usually used in the fire alarm

ü Bimetalic thermostats are devices to measure a constant temperature. Bimetalic thermostats are usually used in electric irons, electric water heaters electric stoves and so on

•         Bimetal thermometers, have function of to measure a temperature. This thermometer does not use liquids as its pointer but they use thin bimetalic plates in the shape spyral.

•         The indicator of motorcycle or car

•         The setting of mirrir glass in  its closed frame will causing a gllas cracked even broken at that time the mirror glass expands bcause it geats heat or the temperature of glass increase.

•         Train rail can bend at that time the rail expands as the cause of sunlight. That can happen because the connection gap of two rail bars is not enough to accommodate rail expansion, so the ends of rail connection push each other and cause rail bends. The bending of train rail can endanger the journey of the train.

THANK YOU