Physics 1104 Sample Exams for Midterm 1. Two sample exams are provided for your use in preparing for your midterm 1 exam.

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1 Physics 1104 Sample Exams for Midterm 1 Two sample exams are provided for your use in preparing for your midterm 1 exam. Just like your actual midterm exam, each sample exam consists of 33 multiple choice questions. You will have 70 minutes to complete the actual 33-question midterm exam. We suggest that you give yourself 70 minutes to work each of these sample exams. Your midterm exam booklet will include a sheet of equations and constants. A copy of this equation sheet will be distributed in class. A key with the sample exam answers is given on the last page of this document. 1

2 Sample midterm 1A 1. Which of the following best demonstrates that increased pressure can bring about a phase change? a) the behavior of a Dippy Duck b) the brittleness of objects cooled in liquid nitrogen c) the cooling sensation of sweating d) the melting of ice under the blade of an ice skate e) the behavior of the liquid in a cryophorus tube (cool tube) when one end of the tube is submerged in liquid nitrogen 2. An electric outlet provides 1,500 watts of power at 120 volts. How many amps of current flow from this outlet? a) amps b) 0.08 amps c) 12.5 amps d) 1,500 amps e) 1,800 amps 3. Of the following, which is a type of thermal energy transfer that occurs as a result of the movement of matter? a) conduction b) convection c) radiation d) sublimation e) condensation 4. An electron absorbs a photon that has 5.0 x joules of energy and the electron moves to a higher energy level. The electron later drops to a lower energy level and emits a photon that has 3.0 x joules of energy. How much more energy must be emitted to satisfy the law of conservation of energy? a) 4.7 x joules b) 4.7 x joules c) 1.7 x joules d) 1.7 x joules e) 4.7 x joules 2

3 Charge Q (in microcoulombs) 5. What is the halving time of the capacitor whose discharge is represented by the graph below? a) 1.5 seconds b) 3.0 seconds c) 4.5 seconds d) 6.0 seconds e) 12.0 seconds Time (in seconds) 6. A 15-amp electric current flows through a heater for two minutes. How many coulombs of charge flow through this heater? a) 7.5 coul. b) 8 coul. c) 30 coul d) 360 coul. e) 1,800 coul. 7. Which of the following is NOT a form of electromagnetic radiation? a) radio waves b) sound waves c) X-rays d) infrared rays e) All of the above are forms of electromagnetic radiation. 3

4 8. You ride an exercise bicycle connected to a generator and light five 50-watt bulbs. If you could generate this much electricity for 2 hours, and were paid $0.12/kWh, how much money would you earn? a) $0.06 b) $0.24 c) $0.30 d) $1.20 e) $ What is the efficiency of an energy conversion process that requires 2,500 joules of energy and produces 1,500 joules of wasted energy? a) 15% b) 33% c) 40% d) 60% e) 100% 10. The equilibrium state of a system is a) the state of minimum entropy of the system. b) the state of maximum entropy of the system. c) the state of minimum energy of the system. d) the state of maximum energy of the system. e) the only state for which the Second Law of Thermodynamics applies. 11. Which of the following situations describes a system that is LEAST likely to be in stable equilibrium with its surroundings? a) a house of cards that has collapsed b) a chair sitting on a level floor c) a pendulum that has come to rest at the bottom of its swinging path d) a baseball flying toward a plate glass window e) a can of soda that has been left open for several hours. 12. The maximum possible efficiency of a heat engine operating between the temperatures of 100 o C and 200 o C is a) 21.1 % b) 26.8 % c) 36.6 % d) 50 % e) 100 % 4

5 13. A heat engine could be 100% efficient if a) the working substance in the heat reservoir is Freon the liquid used in air conditioners. b) the high temperature of the working substance is 100 o C. c) the high temperature of the working substance is 100 kelvin. d) the low temperature of the working substance is zero o C. e) the low temperature of the working substance is zero Kelvin (absolute zero). 14. Gas molecules are placed in a sealed box at a temperature of 300 kelvin. The molecules exert a pressure of 500 N/m 2 on the walls of the box. One half of the gas molecules are removed from the box, and the temperature of the box is increased from 300 K to 900 K. What pressure do the molecules now exert on the box? a) 125 N/m 2 b) 250 N/m 2 c) 500 N/m 2 d) 750 N/m 2 e) 2,000 N/m If the electric company charges 10 cents per kilowatt-hour for electricity, how much will it cost to operate a 75 watt incandescent bulb 5 hours a day for one year? a) $1.37 b) $2.74 c) $3.75 d) $13.69 e) $ A vehicle requires 15 liters of gas to travel 200 kilometers. How many miles can this vehicle travel on one gallon of gas? (1 gallon = liters and 1 mile = kilometers) a) 18.6 miles/gal b) 23.3 miles/gal c) 27.5 miles/gal d) 31.4 miles/gal e) 38.0 miles/gal 5

6 17. A sample of bacteria has a constant doubling time of 10 minutes. If the sample contains 24,000 bacteria now, how many did it contain one hour ago? a) 375 b) 750 c) 1,500 d) 3,000 e) 6, Which of the following statements does NOT demonstrate the fact that a system can be used to do work as the system approaches an equilibrium state? a) A tank of compressed air is used to move a piston in a cylinder. b) A thermoelectric module produces electricity when placed between ice water and hot water. c) A capacitor is used to run a fan. d) Falling water in a waterfall is used to spin a generator and make electricity. e) All of the above examples demonstrate the fact that a system can be used to do work as the system approaches equilibrium. 19. When milk is added to a cup of hot coffee, a) the system of the coffee and milk becomes more ordered. b) the coffee becomes hotter. c) a phase change occurs. d) the entropy of the contents of the cup increases. e) the Second Law of thermodynamics is temporarily violated while the liquids mix. 20. Which of the following forms of energy is based on electric charge? a) electrical b) thermal c) sound d) radiant e) Both a) and d) 6

7 21. How much thermal energy must be added to 10 grams of water at 90 o C to change all of the water into steam at 100 o C? The latent heat of vaporization of water is 540 cal/gram, and the specific heat of water is 1 calorie/gram o C. a) 540 calories b) 740 calories c) 5,400 calories d) 5,420 calories e) 5,500 calories 22. How much work is done when a 20 newton force moves a box across a level floor a distance of 90 cm? a) 4.5 joules b) 18 joules c) 176 joules d) 1,250 joules e) 1,800 joules 23. In order for thermal energy to be transferred as heat from one object to another, the objects must a) have a different thermal conductivity. b) be in contact with each other. c) have different temperatures. d) have different specific heats. e) Both b) and c) are required for thermal energy transfer. 24. Which of the following occurs when liquid water evaporates? a) The temperature of the liquid water increases. b) The temperature of the liquid water decreases. c) The average speed of the liquid water molecules increases. d) The kinetic energy of the liquid water molecules increases. e) The entropy of the system (including both liquid water and water vapor) decreases. 7

8 25. The table below gives the specific heats of some common materials. If you compare equal masses of these materials, an object made of which material would have the greatest heat capacity? Material Specific Heat joules/gram O C Wood Aluminum Water Glass a) wood b) aluminum c) water d) glass e) Their heat capacities would be identical. 26. The hot reservoir of a certain heat engine has an absolute temperature of 400 K. The heat engine currently has a maximum efficiency of 25%. What would be its maximum efficiency of the absolute temperature of BOTH the hot and the cold reservoirs were doubled? a) 12.5 % b) 25 % c) 50 % d) 100 % e) The efficiency cannot be determined without knowing the absolute temperature of the cold reservoir. 27. Which of the following is NOT a correct statement of the second law of thermodynamics? a) The entropy of a system that is in equilibrium with its surroundings remains constant. b) Energy is required to change a system from its equilibrium situation. c) Any system, when left to itself, tends toward equilibrium with its surroundings. d) A system moving toward equilibrium can do work. e) At equilibrium, a system is at its minimum entropy. 8

9 28. A electrical transmission wire carries 100 amps of current and produces 1,500 watts of joule heating. What is the resistance of this wire? a) 0.07 b) 0.15 c) 15 d) 70 e) None of the answers is correct. 29. What is the primary purpose of transformers in the transmission of electricity from a generating plant to the point of use? Transformers a) produce joule heating. b) store electrical energy for later use. c) reduce or increase electrical voltage. d) slow the transmission of electric current. e) can do all of the above. 30. In class, a soda can was filled with a small amount of water. The can was heated on a Bunsen burner and then quickly inverted and placed into a pan of cold water. Which of the following statements best explains what happened to the can and why? a) The can exploded because hot steam had built up inside of it. b) The can exploded because an exothermic chemical reaction occurred in it. c) Hot gas from the can bubbled up through the pan of water for several minutes. d) The can collapsed because the steam that filled the can quickly condensed into water. e) The can collapsed because all of the water drained from the can. 31. Perpetual motion a) is a known source of geothermal energy. b) releases energy in the form of heat. c) occurs only in reversible systems. d) is able to supply large amounts of energy. e) is not possible. 9

10 32. According to the video, NOVA: Absolute Zero, which of the following statements is TRUE? a) Clarence Birdseye was an Ohio farmer who grew green peas and corn. b) The invention of commercial refrigeration had little effect on people s diets. c) Robert Boyle invented a thermometer that used beet juice instead of alcohol in a narrow glass tube. d) James Joule used paddles turning water to show that mechanical motion was converted into heat. e) Fredrick Taylor became rich by selling marble blocks from his New England farm. 33. According to the video, Beyond the Light Switch, Part I, what large source of energy has been found recently in the Marsala shale deposit in southwestern Pennsylvania? a) geothermal b) coal c) oil d) natural gas e) uranium ore 10

11 Sample midterm 1B 1. One kilowatt-hour is equivalent to 3,600,000 joules. How many joules are equivalent to 1,000 kilowatt-hours? a) 7.2 x 10 9 joules b) 3.6 x 10 9 joules c) 7.2 x 10 6 joules d) 3.6 x 10 6 joules e) 3.6 x 10 3 joules 2. What is the change in entropy of a system at a constant temperature of 300 K when 600 calories of thermal energy are added? a) 0.5 cal/k b) 2 cal/k c) 5,000 cal/k d) 180,000 cal/k e) None of the answers is correct. 3. A cup of coffee and a bath tub full of water have the same temperature. Knowing this, you can conclude that a) the coffee has more thermal energy. b) the tub of water has more thermal energy. c) the two have the same thermal energy. d) the molecules in both have the same average kinetic energy. e) Both b) and d) are correct. 4. A heat pump is operating to bring thermal energy into a room at 27 degrees Celsius from outdoors, where the temperature is minus 3 degrees Celsius. What is the coefficient of performance of the heat pump? a) 0.5 b) 1 c) 5 d) 10 e) 20 11

12 5. A total of 20,000 contestants auditioned for an American Idol television show. After each day ended, the number of contestants was reduced by ½. How many contestants remained after the end of the fourth day of auditions? a) 5,000 b) 2,500 c) 1,250 d) 1,000 e) The air in a racing car tire exerts a pressure of 220,000 N/m 2 on the walls of the tire. After being driven at high speed, the temperature of the air inside the tire rises from 300 Kelvin to 330 Kelvin. What maximum pressure does the heated air exert on the walls of the tire? (Consider the volume inside the tire to be constant.) a) 22,000 N/m 2 b) 200,000 N/m 2 c) 242,000 N/m 2 d) 6,600,000 N/m 2 e) You need to know the volume of air inside the tire to answer the question. 7. The fact that two objects of different sizes are at the same temperature means that a) both objects contain the same amount of thermal energy. b) both objects must have the same specific heat. c) thermal energy will be transferred from the larger object to the smaller object. d) thermal energy will be transferred from the smaller object to the larger object. e) no thermal energy will be transferred between the objects. 8. If electricity costs 10 cents per kilowatt-hour, how much does it cost to operate a 1,500 watt toaster oven for 16 minutes? a) 0.4 cents b) 2.4 cents c) 4 cents d) 9.4 cents e) 24 cents 12

13 9. Which of the following is NOT a fundamental force? a) electromagnetic b) strong nuclear c) weak nuclear d) frictional e) All of the above are fundamental forces 10. Which of the following statements is correct? a) Electric current can produce joule heating in conducting wires. b) Batteries store electric charge. c) Electric current is moving electric charge. d) All of the above are correct. e) Only a) and c) are correct. 11. Which of the following correctly lists types of electromagnetic radiation in order from least energy to most energy? a) microwaves, infrared, radio waves, ultraviolet light b) gamma rays, X-rays, ultraviolet light, visible light c) radio waves, infrared, microwaves, visible light d) infrared, visible light, gamma rays, ultraviolet light e) microwaves, infrared, visible light, ultraviolet light 12. In class you placed your hand on a piece of glass, a piece of cork, and a piece of aluminum. All of the materials were at room temperature. Which felt the warmest, and why? a) the glass, because the thermal conductivity of glass is greater than that of the other two materials b) the glass, because the thermal conductivity of glass is lower than that of the other two materials c) the aluminum, because the thermal conductivity of aluminum is lower than that of the other two materials d) the cork, because the thermal conductivity of cork is greater than that of the other two materials e) the cork, because the thermal conductivity of cork is lower than that of the other two materials 13

14 13. The two waves of electromagnetic radiation are pictured below. Which wave has the longer wavelength? Which wave has greater energy? a) Wave A has a longer wavelength and greater energy. b) Wave A has a longer wavelength, and wave B has greater energy. c) Wave B has a longer wavelength and greater energy. d) Wave B has a longer wavelength, and Wave A has greater energy. e) Wave A and wave B have the same energy. Displacement Wave A Wave B Distance 14. If electricity with a voltage of 12,000 volts enters a step up transformer, we would expect the electricity leaving that transformer to have a) a voltage less than 12,000 volts b) a voltage equal to 12,000 volts c) a voltage greater than 12,000 volts d) You need to know the amps of current to answer the question. e) You need to know the location of the transformer to answer the question. 15. During a fishing derby, the number of fish in a pond decreases exponentially with a halving time of 6 hours. If 1,000 fish were in the pond at the beginning of the fishing derby, how many fish will be left after 18 hours? a) 750 b) 500 c) 250 d) 125 e) 67 14

15 16. The fact that a liquid cools by evaporation is related to a) the loss of fast-moving molecules from the liquid. b) the loss of slow-moving molecules from the liquid. c) the absorption of fast-moving molecules from the vapor above the liquid. d) the absorption of slow-moving molecules from the vapor above the liquid. e) the fact that molecules in a liquid move more rapidly than molecules in the vapor above the liquid. 17. How much thermal energy must be added to 2 grams of water to change its temperature by 25 o C? The specific heat of water is 1 calorie/gram o C. a) 12.5 calories b) 25 calories c) 50 calories d) 25 joules e) 50 joules 18. How much joule heating occurs in a wire with a resistance of 0.50 that carries 15 amps? a) 7.5 watts b) 30 watts c) 50 watts d) watts e) 450 watts 19. Which of the following statements is/are FALSE? a) All liquids expand when frozen. b) It is possible to have a phase change directly from a solid to a gas. c) Gases contract when cooled. d) Ice can be melted by increasing the pressure exerted on it. e) Both statements a) and c) are false. 20. Which of the following statements about the entropy of a system is TRUE? a) Entropy is the same as the energy of the system. b) Entropy is the same as the temperature of the system. c) The entropy of a system will decrease if the system is left to itself. d) Entropy cannot be changed when the temperature is held constant. e) Entropy is a measure of the disorder of the system. 15

16 21. Which device could the diagram below represent? a) a heat pump b) a heat engine c) a refrigerator d) an air conditioner e) both c) and d) T H = 293 K T L = 273 K 22. What is the efficiency of the ideal device illustrated in question #21 above? a) 1.1 % b) 6.8 % c) 7.3 % d) 50 % e) 93 % 23. A solar cell requires 100 joules of radiant energy to produce 45 joules of electricity. These 45 joules of electricity are used to light a 15 watt bulb. What is the overall efficiency of this process? a) 1.4% b) 6.8% c) 15% d) 78% e) 99% 16

17 24. How much gravitational potential energy does a 2 kg mass gain by being raised to a height of 4 meters? a) 2 joules b) 8 joules c) 19.6 joules d) 78.4 joules e) None of the answers is correct. 25. Which of the following statements about the entropy of a system is FALSE? a) The entropy of a system increases when the order of the system increases. b) The entropy of a system that is in equilibrium with its surroundings remains constant. c) Any system, when left to itself, tends towards equilibrium with its surroundings. d) Energy is required to change a system from its equilibrium situation. e) Work can be obtained from a system as it moves toward equilibrium with its surroundings. 26. Which of the following is NOT a characteristic of a heat pump? a) When operated backwards, a heat pump can be used to cool a room. b) A heat pump can be used to move thermal energy from one place to another. c) A heat pump requires energy for its operation. d) A heat pump will operate only if it takes thermal energy from a liquid and transfers that thermal energy to a gas. e) All of the above statements are characteristics of a heat pump. 27. Why is electricity transmitted at high voltages? a) to reduce the current needed b) to increase the current needed. c) to reduce joule heating. d) Both a) and b) are correct. e) Both a) and c) are correct. 17

18 28. How long would a 9 amp current need to flow to deliver 1,800 coulombs of charge? a) 0.67 minutes b) 3.3 minutes c) 7.5 minutes d) 200 minutes e) 270 minutes 29. How much thermal energy must be removed from 90 grams of water at 40 degrees Celsius to change all of the water into ice at zero degrees Celsius? The latent heat of freezing water is 80 cal/gram and the specific heat of liquid water is 1 cal/gram degree Celsius. a) 3,600 cal b) 4,800 cal c) 6,000 cal d) 7,200 cal e) 10,800 cal 30. A 5 kg aluminum block at 273 Kelvin sits on top of another 5 kg aluminum block that is at 0 Celsius. Which mechanism most likely describes the thermal energy transfer between the two blocks? a) conduction b) convection c) radiation d) diffusion e) There is no thermal energy transfer. 31. What is the same and what is different when comparing a heat pump with an air conditioner? a) Both have work as an input. b) One has work as an input, the other has work as an output. c) Both move heat from a low temperature location to a high temperature location. d) One moves heat from high to low, while the other moves heat from low to high. e) Choices a) and c) are true for both a heat pump and an air conditioner. 18

19 32. Which of the following statements related to the Second Law of Thermodynamics is FALSE? a) It is impossible to build a perpetual motion machine. b) The amount of entropy that a system can have is unlimited. c) All physical processes are irreversible. d) If a system is in equilibrium with its surroundings, then its entropy is at a maximum. e) The entropy of a physical system left to itself will increase or, if the system is already at its maximum entropy, the entropy will remain the same. 33. What is the change in internal energy of a system if 500 joules of added heat results in 300 joules of work done? a) 1.7 joules b) 200 joules c) 800 joules d) 1,250 joules e) 150,000 joules 19

20 Answers to Sample Midterms 1A and 1B Question Number Mid 1A Answers Question Number 1 d 1 b 2 c 2 b 3 b 3 e 4 b 4 d 5 b 5 c 6 e 6 c 7 b 7 e 8 a 8 c 9 c 9 d 10 b 10 e 11 d 11 e 12 a 12 e 13 e 13 b 14 d 14 c 15 d 15 d 16 d 16 a 17 a 17 c 18 e 18 d 19 d 19 a 20 e 20 e 21 e 21 b 22 b 22 b 23 c 23 c 24 b 24 d 25 c 25 a 26 b 26 d 27 e 27 e 28 b 28 b 29 c 29 e 30 d 30 e 31 e 31 e 32 d 32 b 33 d 33 b Mid 1B Answers 20