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# Thermal expansion

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• examples for practice..

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• can i get answers for the exercises plz

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### Thermal expansion

1. 1. ThermalExpansionLinear and Volume
2. 2. Objectives• Define thermal expansion• Identify the factors affecting thermal expansion• Solve sample problems involving linear expansion and volume expansion• Cite everyday applications of the concepts
3. 3. Thermal Expansion• Change in the dimension(s) of a substance due to change in temperature
4. 4. Factors affecting THERMAL EXPANSION
5. 5. Temperature• Higher change in temperature, the higher the expansion• ΔT for the symbol
6. 6. Kind of Material• Quantified by a constant value for coefficient of thermal expansion for some materials• The higher the coefficient, the higher the expansion• Symbol used - α
7. 7. Original Dimension• Greater original dimension, greater the expansion.• L for linear• A for area• V for volume
8. 8. ΔL = α·L0·ΔTChange in Coefficient of Originaldimension expansion length Change in temperature
9. 9. Types ofEXPANSION
10. 10. Linear Expansion- the expansion in length of solid bodies onheating ΔL = α·L0·ΔT L0 ΔL
11. 11. Coefficients ofThermal Expansionfor Some materials
12. 12. LINEAR MATERIAL COEFFICIENT GLASS 8.5 MERCURY 26 ALUMINUM 24 COPPER 17Example: BRASS 19 IRON 11.1α = 12 X 10-6 1/K PLATINUM 9 GOLD 14 SILVER 18 STEEL 11.0 ~ 13.0 CONCRETE 12 RUBBER 77
13. 13. Opening a tight Jar lid
14. 14. Volume Expansion- sometimes called the “cubic expansion” ΔL = 3α·L0·ΔT or V0 ΔL = β·L0·ΔT or ΔV ΔV = β·V0·ΔT
15. 15. Exercises
16. 16. 1. During winter, why is itimportant to protect water pipes?
17. 17. 2. Why is itadvisable to allowtelephone lines tosag when stringingthem betweenpokes in summer?
18. 18. 3. What is the change in length ofa metal rod with an initial lengthof 2 meters, a coefficient ofthermal expansion 0.00002 /K anda temperature change of 20 K?
19. 19. 4. Suppose you have a 0.05 Lcontainer made of glass that is at283 K. You raised its temperatureto 303 K. By how much will itsvolume increase? (glass = 25.5x10-6 1/K)
20. 20. 5. A steel rail is 24.4mlong. How much does itexpand during a daywhen the lowtemperature is 291 Kand high temperature is306 K? (Steel = 12 x10 1/K) -6
21. 21. 6. The length of a brass bar is 150cm at 40 C. What will be its lengthat 100 C?(α = 19 x 10-6/K)
22. 22. 7. An aluminum flag pole is20.0 m tall on a -15 C winter’sday. How much higher will theflag fly from the pole on a hot42 C summer day?
23. 23. 8. What amount of change intemperature did a 0.25 kg coppermetal undergo when it is initially5.0 m long and expanded by0.00002 m?
24. 24. 9. A glass flask whose volume is 1000.0cm 3 at 0.0 C is completely filled withmercury at this temperature. Whenflask and mercury are warmed to 80.0 C, 12.5 cm3 of mercury overflow.Compute the coefficient of volumeexpansion of the glass.