PLEASE DO NOT LOOK AT THE CONTENTS OF THIS EXAM, OTHER THAN THIS COVER PAGE, UNTIL TOLD TO DO SO.

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1 Physics 1110 Energy Fall 2013 Midterm Exam - November 21, Page 1of 6 Name: Solutions Mail ID: PLEASE DO NOT LOOK AT THE CONTENTS OF THIS EXAM, OTHER THAN THIS COVER PAGE, UNTIL TOLD TO DO SO. This exam is closed book, but you may use one sheet of paper (both sides) with hand-written notes. Useful information 1 gallon of gasoline = J 1 euro = $ Watts 1 gallon = 3.79 liters σ = m 2 K ρ 4 air = 1.29 kg/m 3 Area of sphere = 4 π r 2 1 barrel = 42 gallons 1 cubic foot natural gas = 10 3 BTU s 1 mile = km Directions On this exam booklet, please fill out your name, address, the date, and sign the pledge. On your bubble sheet, please fill in your name and the date in the spaces provided. Under Test please write Midterm, version a, and under Class name/abbreviation please write Physics In the column on the right-hand side PLEASE BE CERTAIN to bubble in your UVa computing ID. Each multiple choice question has one and only one correct answer. When you are finished, please place your bubble sheet underneath this cover page before you hand it in. You do not need to hand in your cheat sheet. On my honor as a student of the University of Virginia I have neither given nor received aid on this exam. I have read all of the exam rules stated above, and have completed this exam honestly, according to those rules. Signed: Date:

2 Midterm Exam November 21, 2013 Page 2 of 6 1. What is the approximate increase in CO 2 in the atmosphere since the beginning of the industrial revolution? a. 10% b. 20% c. 40% d. 100% 2. The most plentiful renewable energy source on the planet is solar. What is the second most plentiful? a. Hydroelectric. b. Waves. c. Geothermal. d. Wind. 3. When considering the fraction of electricity that is generated by wind, which country is NOT in the top five? a. Spain b. Portugal c. United States d. Ireland 4. What is a PTC? a. Production Tax Credit. b. Primary Thermal Conversion. c. Refers to the Power-To-Carbon ratio. d. Process Thermal Cycle 5. Which of the following is closest to the land area needed to produce all of the electricity in the U.S. using solar power? a. The area of Massachusetts. b. The area of Alaska. c. The area of California. d. The area of Texas. 6. Which country has the third largest resources of coal? a. Russia b. China c. Australia d. India

3 Midterm Exam November 21, 2013 Page 3 of 6 7. At our present rate of consumption, which of the following represents the approximate length of time it would take the U.S. to exhaust its natural-gas resources (at least as those resources are currently understood)? a. 10 years. b. 30 years. c. 100 years d. 300 years 8. A utility decides to construct a solar-thermal electricity generating facility with a peak power of 750 MW. Assume a conversion efficiency of 25%, and that the peak intensity of sunlight on a surface directly facing the sun is 1 kw/m 2. Which of the following describes the collective surface area of all the collectors? a km x 0.43 km Hot reservoir, T b km x 0.87 km H c km x 1.73 km d. 2.0 km x 2.0 km Q H 9. Consider the diagram at right illustrating a heat engine. Assume that during asingle cycle, Q H = 1200 J and that the efficiency of the heat engine is 30%. How much useful work is done during each cycle? a. 360 J b. 600 J c. 720 J d J Q C Cold reservoir, T C 10. There is currently a boom in U.S. domestic oil production. What is predominantly responsible? a. In situ extraction of bitumen from tar sands. b. Surface mining of bitumen from tar sands. c. Deep ocean drilling in the Gulf. d. Hydraulic fracturing and horizontal drilling in shale formations. 11. A space heater draws 1200 Watts out of the wall. How much energy does it consume in 12 minutes? a J b. 100 J c J d. 14,400 J 12. What limits the efficiency of a windmill? a. There is no limit. In principle the efficiency could approach 100%. b. The Carnot efficiency. c. Entropy. d. None of the above. work

4 Midterm Exam November 21, 2013 Page 4 of Which renewable energy source is responsible for the largest amount of end use consumption in the United States? a. Biofuels b. Wind c. Hydroelectric d. Wood 14. A Prius uses 1.35 gallons of gasoline while traveling on a highway at 65 mph over the course of 1 hour. What is the rate at which thermal energy is being released by the fuel? a kw b kw c kw d W 15. A Prius gets 50 miles per gallon. What is its mileage in kilometers per liter? a. 8.2 km/liter b km/liter c. 118 km/liter d. 305 km/liter 16. A windmill produces 500 kw when the wind speed is 5 m/s. What is the output power of the windmill when the wind speed is 10 m/s? You may assume that the windmill has the same efficiency at the two wind speeds being considered. a. 500 kw b kw c kw d kw 17. Which of the following is the most important factor limiting the rate of production of synthetic crude from Canadian tar sands? a. The fact that the only method for extracting bitumen is strip mining. b. The desire of Canadians to preserve the resource for use in Canada. c. Locating deposits large enough to be developed profitably. d. The availability of the energy needed to get the bitumen out of the ground. 18. What is a potential advantage of the power tower design over other approaches to producing electricity from solar energy? a. It can produce electricity at night. b. It uses more efficient photovoltaics than conventional solar panels. c. It works better than other solar power approaches when the sky is hazy or partly cloudy. d. All of the above.

5 Midterm Exam November 21, 2013 Page 5 of What con(s) is(are) associated with the current use of ethanol as a biofuel. a. It takes nearly as much energy to make the ethanol as you get out of the ethanol. b. The use of ethanol has caused food prices to rise significantly. c. The process of producing ethanol is nowhere near being carbon neutral d. All of the above. 20. An interesting feature of IGCC technology is that a. it could help with the production of ethanol. b. it could help with the production of biodiesel. c. it would enable the more efficient use of natural gas. d. it can also be adapted to solar energy. 21. When Feynman talks about the law of the lever what principle or idea is he trying to illustrate? a. The universal law of gravity. b. The conservation of energy. c. Mechanical advantage. d. That mathematics is the appropriate language of physics. 22. Which of the following can be produced using coal? a. Gas for lighting. b. Gas that can be used to produce electricity. c. Liquid fuel. d. All of the above 23. Most biodiesel in the U.S. is produced using soybeans as a feedstock. Can this approach be used to solve all U.S. domestic needs for transportation fuel? a. No, because it takes more energy to produce the biodiesel than is contained in the fuel. b. No, because there is not sufficient crop land to support such an expansion. c. Yes, but at present, it is much too expensive. d. Yes, and the production of biodiesel from soybeans is growing at a very fast pace. 24. Which of the following can be considered an external combustion engine? a. A gasoline engine in a typical automobile b. A diesel engine in a typical automobile c. A solar-thermal electrical power generating plant. d. All of the above.

6 Midterm Exam November 21, 2013 Page 6 of Which of the following statements is true? a. All machines are heat engines of one sort or another. b. The operation of a heat engine raises the entropy of the universe. c. Internal combustion engines are heat engines, but external combustion engines are not. d. A combined cycle power generation plant exceeds the Carnot efficiency by extracting energy from waste heat. 26. Which of the following has the strongest greenhouse effect? a. Earth. b. The Earth s moon. c. Venus. d. Mars. 27. If we were to argue that there is an energy crisis in the United States, what might we point to as the most challenging aspect of the crisis? a. We are fast running out of fossil fuels, regardless of whether they are produced domestically or imported. b. We are fast running out of fossil fuels that are produced domestically. c. It is becoming difficult to figure out how to generate enough electricity. d. It is becoming more difficult and/or expensive to produce liquid fuels for transportation.