1. Phys 150 Lecture 11 Please sit together in pairs: –Onyema and Honglu –Alejandra and Sean –Chris and Lin –Rachel and Anwen –John F. and Mengyue –Walter and Melissa –Max and Zhongyun –Matt and Anna –Amanda and Kaijun –Pauline and Erich –Jacob and Irfan –John W. and Michael –Jennifer and Jiayuan –Alexandra and Erica –Emmanuel and Dian –Robert and David –Andrew and Shiying

2. Phys 150 Lecture 22 Announcements Chapters 1 and 2 are available online (see the 150 web page). There will be a Quiz on Chapter 1 on Tuesday at the beginning of class. Homework 1 is due on Sunday at midnight. Please go to the 150 web page and click on Course Schedule. i>clickers are required starting Tuesday. Please register via the 150 web page.

3. Phys 150 Lecture 23 Explosions Cannon Rapidly expanding hot gas

4. Phys 150 Lecture 24 Explosions Cannon Rapidly expanding hot gas Comet Shoemaker-Levy 9 1994

5. Phys 150 Lecture 25 Explosions Extinction of dinosaurs 65 million years ago Kinetic energy = energy of motion = ½ mv 2

6. Phys 150 Lecture 26 Power 60 Watt incandescent light bulb –Most of the power is producing heat, not light 13 Watt Compact Fluorescent Light (CFL) –Same light output with 1/4 the energy use 10 Watt Light Emitting Diode (LED) –Same light output with 1/6 the energy use! Power = Energy/Time Watt = Joules/sec Bulbs

7. Phys 150 Lecture 27 Power 60 Watt incandescent light bulb –Most of the power is producing heat, not light 13 Watt Compact Fluorescent Light (CFL) –Same light output with 1/4 the energy use 10 Watt Light Emitting Diode (LED) –Same light output with 1/6 the energy use Bulbs

8. Phys 150 Lecture 28 Electric energy A 10 Watt LED bulb running continuously for one year (24 hrs/day x 365 days/yr = 8760 hours) uses 10 Watts x 8760 hours = 87,600 Watt-hours = 87.6 kilowatt-hours kilowatt-hour (kWh) is a commonly used unit of energy (kilowatt = 1000 Watts)

9. Phys 150 Lecture 29 Energy units Calorie (Cal) – food and chemistry kilowatt-hour (kWh) - electricity British Thermal Unit (BTU) – heating/cooling Joules (J) – science 1000 Cal ≈ 1 kWh ≈ 4000 BTU

10. Phys 150 Lecture 210 i>clicker question A typical house in the US requires about a kW of electric power. How much electric power do you need to power a million homes? A.kilowatt B.Megawatt C.Gigawatt D.Terawatt

11. Phys 150 Lecture 211 i>clicker question A typical house in the US requires about a kW of electric power. How much electric power do you need to power a million homes? A.kilowatt (kW) = 1000 W = 10 3 W B.Megawatt (MW) = 1,000,000 W = 10 6 W (million) C.Gigawatt (GW) = 1,000,000,000 W = 10 9 W (billion) D.Terawatt (TW) = 1,000,000,000,000 W = 10 12 W (trillion) A large electric power plant generates about a Gigawatt of electric power

12. Phys 150 Lecture 212 i>clicker question A typical home in the US requires about a kW of electric power (without AC). How much electric power do you need to power a million homes? kW x 1,000,000 = 1000 W x 1,000,000 = 1,000,000,000 W = Gigawatt kW x 10 6 = 10 3 W x 10 6 = 10 9 W = Gigawatt Calculator: 1 EE 3 x 1 EE 6 = 1 09

13. Phys 150 Lecture 213 Types of Energy Chemical energy Heat energy = Thermal energy Kinetic energy = energy of motion = ½ mv 2 Electric energy Light energy Nuclear energy ≈ 10 6 x chemical energy

14. Phys 150 Lecture 214 Light energy Light energy (solar energy) Solar motor

15. Phys 150 Lecture 215 i>clicker question The amount of power in one square meter of sunlight (with the sun directly overhead) is about A.1000 BTU B.1000 Calories C.1 kWh D.1 kW

16. Phys 150 Lecture 216 i>clicker question The amount of power in one square meter of sunlight (with the sun directly overhead) is about A.1000 BTU B.1000 Calories C.1 kWh D.1 kW meter 2 of sunlight ≈ 1 kW

17. Phys 150 Lecture 217 Solar automobiles Typical automobile needs 50 – 400 hp Solar car meter 2 of sunlight ≈ 1 kW ≈ 1 hp

18. Phys 150 Lecture 218 Solar airplanes meter 2 of sunlight ≈ 1 kW ≈ 1 hp Zephyr – flew for 2 weeks Zephyr

19. Phys 150 Lecture 219 1 kW ≈ 1 hp ≈ meter 2 of sunlight

20. Phys 150 Lecture 220 i>clicker question The amount of power in one square kilometer of sunlight (with the sun directly overhead) is about A.1 kW B.1 MW C.1 GW D.1 TW

21. Phys 150 Lecture 221 i>clicker question The amount of power in one square kilometer of sunlight (with the sun directly overhead) is about A.1 kW B.1 MW C.1 GW D.1 TW –km 2 = 10 3 m x 10 3 m = 10 6 m 2, so –km 2 sunlight = 10 6 x kW = 10 6 x 10 3 W = GW –Same as a large power plant

22. Phys 150 Lecture 222 Solar Photovoltaic (PV) cells Inexpensive ones are 15% efficient Expensive ones are 40% efficient $325Very expensive