# Ch12 - Chapter 12 The Laws of Thermodynamics CHAPTER 12 1 A...

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Chapter 12, The Laws of Thermodynamics C HAPTER 12 1. A system is acted on by its surroundings in such a way that it receives 50 J of heat while simultaneously doing 20 J of work. What is its net change in internal energy? a. 70 J b. 30 J c. zero d. 30 J 2. The volume of an ideal gas changes from 0.40 to 0.55 m 3 although its pressure remains constant at 50 000 Pa. What work is done on the system by its environment? a. –7 500 J b. 200 000 J c. 7 500 J d. 200 000 J 3. In an isothermal process for an ideal gas system (where the internal energy doesn’t change), which of the following choices best corresponds to the value of the work done on the system? a. its heat intake b. twice its heat intake c. the negative of its heat intake d. twice the negative of its heat intake 4. A heat engine exhausts 3 000 J of heat while performing 1 500 J of useful work. What is the efficiency of the engine? a. 15% b. 33% c. 50% d. 60% 5. A heat engine operating between a pair of hot and cold reservoirs with respective temperatures of 500 K and 200 K will have what maximum efficiency? a. 60% b. 50% c. 40% d. 30% 146

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Chapter 12, The Laws of Thermodynamics 6. Which of the following choices best corresponds to what is required by the second law of thermodynamics for any process taking place in an isolated system? a. entropy decreases b. entropy remains constant c. entropy increases d. entropy equals work done on the system 7. Which of the following choices is an appropriate unit for measuring entropy changes? a. J K b. N K c. J/s d. J/K 8. An electrical power plant manages to send 88% of the heat produced in the burning of fossil fuel into the water-to-steam conversion. Of the heat carried by the steam, 40% is converted to the mechanical energy of the spinning turbine. Which of the following choices best describes the overall efficiency of the heat-to-work conversion in the plant (as a percentage)? a. greater than 88% b. 64% c. less than 40% d. 40% 9. If one could observe the individual atoms making up a piece of matter and note that during a process of change their motion somehow became more orderly, then one may assume which of the following in regard to the system? a. increases in entropy b. decreases in entropy c. gains in thermal energy d. positive work done on 10. A 1.0-kg chunk of ice at 0 ° C melts, absorbing 80 000 cal of heat in the process. Which of the following best describes what happens to this system? a. increased entropy b. lost entropy c. entropy maintained constant d. work converted to energy 147
Chapter 12, The Laws of Thermodynamics 11. According to the first law of thermodynamics, the sum of the heat gained by a system and the work done on that same system is equivalent to which of the following?

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## This note was uploaded on 07/25/2008 for the course PHY 231C taught by Professor Pratt during the Spring '06 term at Michigan State University.

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Ch12 - Chapter 12 The Laws of Thermodynamics CHAPTER 12 1 A...

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