REAL WORLD APPLICATION OF THERMAL EXPANSION

APPLCIATION OF THERMAL EXPANSION

1. 1 Uses of Bacteria in Food Industry Real World Application of Thermal Expansions of Solids

2. 2 INTRODUCTION Democritus Leucippus Democritus Leucippus Thermal Expansion It is a well-known phenomenon now that substances expand on heating and contract on cooling. If you heat a body, it alters its dimensions. Depending on the shape of the body . The expansion produced in the matter due to the absorption of heat energy is called Thermal Expansion . Whenever, any substance ( solid, liquid, or gas) is heated, its volume increases. The expansion in matter is divided into three classes : Linear Expansion : The increase in length of a solid when heated, is called linear expansion. Superficial Expansion: The increase in area of a solid when heated is called superficial expansion. Cubical Expansion: The increase in volume of a substance ( solid, liquid& gas) when heated is called c ubical expansion .

3. 3 Expansion of Solids – An Experiment Gravesande’s Ring and Ball Experiment Ring and ball apparatus in a 1912 scientific instrument catalog for performing Gravesande's experiment, a simple experiment demonstrating  thermal expansion . It consists of a small metal ball suspended by a chain from a stand, with a metal ring below it . The external diameter of the ball is equal to the internal diameter of the ring, such that the ball can easily pass through the ring. The ring is made just big enough so when both pieces are at the same temperature, the ball fits through the ring. However, when the ball is heated by dipping it in boiling water, or playing a spirit lamp flame over it, the metal expands and it can no longer fit through the ring. From the above experiment, it is concluded that the solids expand on heating . Now allow the ball to cool to room temperature and it can be seen that the ball again pass through the ring. This proves, that the solids contract on cooling.

4. 4 4 Uses of Bacteria in Food Industry Real World Application Of Thermal Expansions of Solids

5. 5 Application of Linear Expansion of Solids Linear expansion is the expansion in the length of the substance which is subjected to increasing temperature. Linear expansion mostly takes place in solids. Applications : Mounting of Iron Rim on Wooden cart Wheel : The Iron rim to be mounted on wooden cart wheel has a slightly smaller diameter than wooden wheel. The iron rim is heated so that it expand. When its size becomes larger than wooden wheel it is slipped on the wheel. After that cold water is poured on the wheel so that on cooling the rim contracts and holds the wooden wheel tightly. It is for the same reason, the Tonga drivers pours cold water over iron rims during hot summer which prevents the iron rim from loosening its grip over the wooden wheel. Laying of Rail Tracks: Rails are made of steel, which expands on heating and contract on cooling. If rails are fixed tightly leaving no space for expansion or contraction, these will bend outward in summer and will result in derailment of trains. To avoid this, small gaps are left between the rails. The rails are then joined by fishplates. In summer the gaps get smaller and winter bigger, but rail by itself remains straight.

6. 6 Application of Linear Expansion of Solids The clocks regulated with pendulum require adjustment during summer and winter: The pendulum of clocks expand in summer and contract in winter, therefore, they lose time in summer and gain time in winter. In order that the clocks should give correct time, the pendulums are made from invar which is an alloy having vey small coefficient of linear expansion in some clocks, compensating pendulums are used. A compensating pendulum is made of a number of iron and brass rods joined in such a way that the length of pendulums remains contacts even if there is a change in temperature. Mounting of Bridges: The girders supporting the bridge are not fixed in the walls of the pillars.it is because they expand on heating and contract on cooling and in doing so, can break pillars, then the bridge can collapse. Because of this, the girders are mounted on rollers, leaving a small space in between for expansion or contraction. That’s how the bridge is saved from a possible collapse. It is for the same reason that small spaces are left behind the walls, while mounting the girders. So as to allow for expansion and contraction.

7. 7 Application of Linear Expansion of Solids Laying of Telephone and Electric Transmission Line : The metallic wires tend to expand during summer and sag down. They may come in contact with other wires during storm, causing a serious breakdown. In winter they contract and can break. Thus, when the telephone or telegraph wires are laid in summer, they are kept slightly loose so as to allow for contraction in winter. Similarly, if they are laid in winter they are kept very tight so as to allow expansion during summer. Laying of Cement Floor: Cement floor is not laid as one block. It is because it expands during summer. As there will not be any space for expansion, therefore, it will crack. Instead floor is laid in small blocks leaving a very small space in between the blocks. This is in turn, allows for expansion, and hence the floor does not crack. Breaking of Glass : When milk is poured into a thick walled glass vessel at room temperature, the inner surface of the vessel gets expanded, while the outer surface remains at room temperature. Thus there is no expansion on the outer surface. Due to uneven expansion in the vessel, the glass cracks.

8. 8 Application of Linear Expansion of Solids Bimetallic Strip and Fire Alaram : Plates of two different metals which are riveted together at a number of points in such a way that they can not slide on being heated or cooled for a “Bimetallic Strip” . The bimetallic strip figure shows a brass-invar ( an alloy of iron) at room temperature in straight position. When this is heated, the brass expands more as compared to invar. This unequal expansion bends the strip, the brass takes the outer edge of the bend and invar takes the inner edge of the bend. On cooling the bimetallic strip below the room temperature, the brass contracts more than the invar. Thus the bimetallic strip bends and the invar takes the outer edge of the bend and brass takes the inner edge of the bend. Application: Automatic Fire Alarm - The bimetallic strip is used in Fire Alarm. Incase of fire the bimetallic strip gets heated and bends. The brass expands more than invar and rise up and a electrical contact is established resulting the bell starts ringing giving an alarm. - Bimetal thermometers work on  the principle that different metals expand at different rates as they are heated . They are used in Oven, air conditioner in industrial apparatus like refineries, hot wires, heater, tempering tanks etc.

9. 9 Application of Superficial Expansion of Solids Superficial Expansion of Solid : When it gets heated, its length and breadth get expensive. This is nothing but superficial expansion. an increase in the dimension(only length and breadth) of the body because of heating is known as superficial expansion. So an  increase in area that is length and bread on heating  is called a superficial expansion. Removing Tight Lids of Glass Jar: To open the lid of a glass jar that is tight enough, it is immersed in hot water for a minute or so. Metal cap expands and loose. It would now be easy to turn it to open. The high temperature water causes the metal lid and glass jar to expand. But glass has a low coefficient expansion than the material of the lid. Hence the lid expands more than the glass jar and the lid can be easily removed. To Pass a Nail Through Hole in Metal Plate: To pass nail thorugh a metal plate having a hole of a diameter slightly less than that of the nail, the plate is heated. So that the diameter of hole increases and the nail can easily pass through it.

10. 10 Application of Volumetric Expansion of Solids Volumetric Expansion of Solid : Volumetric expansion is the expansion in the volume of the substance which is subjected to increasing temperature. For an open solid, volumetric expansion refers to the expansion of the volume enclosed by it . Application: Riveting of two Metal Plates: Two metal plates can be jointly tightly together by a process called riveting. Rivets are heated to red hot condition and are forced through coaxial holes in the two plates. The end of hot rivets is then hammered and shaped. On cooling, the rivets contracts and bring the plates tightly gripped to each other. Design of Air Craft: The aircraft expands by 15-25 centimeter during its flight due to increase in temperature on account of heat created by friction with air. Designers used rollers ( separators) to isolate the cabin and passenger area from the body of aircraft so that the expansion does not rip the plane apart.

11. 11 Thank You Bibliography : https:// thefactfactor.com/facts/pure_science/physics/applications-of-expansion-of-solids https:// www.vedantu.com/question-answer/name-three-types-of-thermal-expansion https:// www.sciencedirect.com/topics/engineering/linear-coefficient-of-expansion https:// en.wikipedia.org/wiki/Thermal_expansion https:// www.google.com/search?bih=577&biw=1280&sxsrf=AOaemvKloXSH0_ilW9sW92h3uB5FyU2jgQ:1632141184036&source=univ&tbm=isch&q=thermal+expansion+of+solids&hl=en-GB&sa=X&ved=2ahUKEwidh_3bx43zAhVG7XMBHSiVCF4QjJkEegQIIRAC https://ncert.nic.in/ncerts/l/keph203.pdf Acknowledgement : I wish to express my deep gratitude and sincere thanks to the Principal, Mrs Sudha Menon , North Point School for her encouragement and facilities that she provided for this project work . I extend my hearty thanks to Mrs.Gauri Kulkarni Physics teacher , who guided me to the successful completion of this project. I take this opportunity to express my deep sense of gratitude for her invaluable guidance, constant encouragement, immense motivation, which has sustained my efforts at all the stages of this Project work… I can’t forget to offer my sincere thanks to parents and also to my sister who helped me to carry out this project work successful and for their valuable advice and support, which I received from them time to time….