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Phys 150 Lecture 20

Please sit together in pairs: Mike A. and Disha Barney and Efrain Thomas and Da Glenn and Heran Ann and Joe Serruto Johnny and Yiran Korey and Steve T. Will and Joey B. Michael W. and Andrea Zach and Stephen H. Casey and Qihan Audrey and Nicole Lisette and Ed Erica and Zhenmin.

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Phys 150 Lecture 20

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  1. Please sit together in pairs: Mike A. and Disha Barney and Efrain Thomas and Da Glenn and Heran Ann and Joe Serruto Johnny and Yiran Korey and Steve T. Will and Joey B. Michael W. and Andrea Zach and Stephen H. Casey and Qihan Audrey and Nicole Lisette and Ed Erica and Zhenmin • Mikhail and Taehoon • Valerie and Shenheng • Kevin and Matt R. • Ally and Grant • Matt M. and Evan • Morgan and Rebecca • Laura and Katherine • Lauren and Joe Sebek • Mikey O. and Quanbiao • Hannah and Charlie • Jim and Lu • Nick and Ashkan • Ben and Naichen • Nik and Dale Phys 150 Lecture 20 Phys 150 Lecture 27 1

  2. Announcements Check your grades on the gradebook and email me if there are any problems. Final Exam is Friday, Dec. 14, 7:00 PM to 10:00 PM in this room (Loomis 151). Covers Chapters 1-11 and Chapters 6, 25, 20 from MacKay (see the Phys 150 web page). One essay on the final exam will be about Climate Change. The other essay will be on electromagnetic radiation (visible light, IR, X-rays, etc.) and nuclear radiation (alpha, beta, gamma). Phys 150 Lecture 27 Phys 150 Lecture 25 2 26-Apr-2011

  3. Holiday presents • Physics for Future Presidents (Richard Muller, the popular book for the layman). • Energy for Future Presidents (R. Muller) • The Long Thaw (David Archer) Phys 150 Lecture 27

  4. A typical 1929 house Phys 150 Lecture 27 Phys 150 Lecture 27 4 3-May-2011

  5. i>clicker question When retrofitting a house, what’s the most important step? Sealing cracks Adding insulation Replacing windows Phys 150 Lecture 27 Phys 150 Lecture 27 5 3-May-2011

  6. i>clicker question When retrofitting a house, what’s the most important step? Sealing cracks – reduce air infiltration Adding insulation Replacing windows - Flow of hot or cold air is “convection” Phys 150 Lecture 27 Phys 150 Lecture 27 6 3-May-2011

  7. Air sealing • Attic Basement Phys 150 Lecture 27

  8. i>clicker question When this 1929 house was built, it had No insulation in the walls 2 inches of wool insulation 3 inches of fiberglass insulation 3.5 inches of cellulose insulation Phys 150 Lecture 27 Phys 150 Lecture 27 8 3-May-2011

  9. i>clicker question When this 1929 house was built, it had No insulation in the walls 2 inches of wool insulation 3 inches of fiberglass insulation 3.5 inches of cellulose insulation Original heating system was coal burning furnace Current heating system burns natural gas Insulation reduces heat “conduction” (and also aids air sealing) Phys 150 Lecture 27 Phys 150 Lecture 27 9 3-May-2011

  10. Dense pack cellulose • 3.5 inches dense pack cellulose • R = 13 (R = resistance to heat conduction) Phys 150 Lecture 27

  11. i>clicker question When this 1929 house was built, it had No insulation in the attic 2 inches of wool insulation 3 inches of fiberglass insulation 3.5 inches of cellulose insulation Phys 150 Lecture 27 Phys 150 Lecture 27 11 3-May-2011

  12. i>clicker question When this 1929 house was built, it had No insulation in the attic 2 inches of wool insulation – “rock wool” 3 inches of fiberglass insulation 3.5 inches of cellulose insulation - Rock wool is similar to fiberglass Phys 150 Lecture 27 Phys 150 Lecture 27 12 3-May-2011

  13. Loose fill cellulose • 13 inches loose fill cellulose • R = 49 (R = resistance to heat conduction) Phys 150 Lecture 27

  14. Phys 150 Lecture 27

  15. i>clicker question The result of air sealing and adding insulation to the walls and attic of this 1929 house is (gas furnace) 10% reduction in gas, no reduction in electricity 20% reduction in gas, no reduction in electricity 20% reduction in gas, 10% reduction in electricity 30% reduction in gas, 30% reduction in electricity Phys 150 Lecture 27 Phys 150 Lecture 27 15 3-May-2011

  16. i>clicker question The result of air sealing and adding insulation to the walls and attic of this 1929 house is (gas furnace) 10% reduction in gas, no reduction in electricity 20% reduction in gas, no reduction in electricity 20% reduction in gas, 10% reduction in electricity 30% reduction in gas, 30% reduction in electricity The blower on the gas furnace uses electricity Phys 150 Lecture 27 Phys 150 Lecture 27 16 3-May-2011

  17. Holiday present Home energy audit ($50) Act on Energy (Ameren Illinois) Central and Southern Illinois 866 838 6918 Smart Ideas (Com Ed) Chicago and Northern Illinois 888 806 2273 Audit is performed by an independent third party (Conservation Services Group) There are financial incentives for many upgrades Phys 150 Lecture 27 Phys 150 Lecture 27 17 3-May-2011

  18. i>clicker question Modern well-insulated windows are coated with a material that • reflects IR radiation • absorbs IR radiation • reflects UV radiation • absorbs UV radiation Phys 150 Lecture 27

  19. i>clicker question Modern well-insulated windows are coated with a material that • reflects IR radiation –ITO (Indium Tin Oxide) • absorbs IR radiation • reflects UV radiation • absorbs UV radiation – ordinary glass • Windows typically have R ≈ 3 (or U = 1/R ≈ 1/3) Phys 150 Lecture 27

  20. i>clicker question In the winter, if you turn down your thermostat at night (but put it back to normal during the day), you will • use less energy • use more energy • use less energy at night but more during the day, with no net change in energy use • pay less for energy because natural gas is more expensive at night Phys 150 Lecture 27

  21. i>clicker question In the winter, if you turn down your thermostat at night (but put it back to normal during the day), you will • use less energy • use more energy • use less energy at night but more during the day • pay less for energy because natural gas is more expensive at night - Heat loss is proportional to temperature difference between inside and outside Phys 150 Lecture 27

  22. i>clicker question Which of these is NOT a unit of energy? • BTU • Calorie • kW • Joule Phys 150 Lecture 27

  23. i>clicker question Which of these is NOT a unit of energy? • BTU – beware: furnaces, etc., are rated in BTU – but they really mean BTU/hr • Calorie • kW –power (kWh is unit of energy) • Joule Phys 150 Lecture 27

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