# Ap Assignment

Topics: Temperature, Heat engine, Carnot cycle Pages: 6 (1888 words) Published: May 14, 2013
Focus On Concepts
Section 15.3  The First Law of Thermodynamics
1. The first law of thermodynamics states that the change U in the internal energy of a system is given by U = Q - W, where Q is the heat and W is the work. Both Q and W can be positive or negative numbers. Q is a positive number if ________, and W is a positive number if ________.  (a) the system loses heat; work is done by the system  (b) the system loses heat; work is done on the system  (c) the system gains heat; work is done by the system  (d) the system gains heat; work is done on the system Section 15.4  Thermal Processes

4. The drawing shows the expansion of three ideal gases. Rank the gases according to the work they do, largest to smallest.  (a) A, B, C  (b) A and B (a tie), C  (c) B and C (a tie), A  (d) B, C, A  (e) C, A, B

6. The pressure–volume graph shows three paths in which a gas expands from an initial state A to a final state B. The change
in internal energy is the same for each of the paths. Rank the paths according to the heat Q added to the gas, largest to smallest.  (a) 1, 2, 3  (b) 1, 3, 2  (c) 2, 1, 3  (d) 3, 1, 2  (e) 3, 2, 1

Section 15.5  Thermal Processes Using an Ideal Gas
8. An ideal monatomic gas expands isothermally from A to B, as the graph shows. What can be said about this process?  (a) The gas does no work.  (b) No heat enters or leaves the gas.  (c) The first law of thermodynamics does not apply to an isothermal process.  (d) The ideal gas law is not valid during an isothermal process. (e) There is no change in the internal energy of the gas.

10. A monatomic ideal gas is thermally insulated, so no heat can flow between it and its surroundings. Is it possible for the temperature of the gas to rise?  (a) Yes. The temperature can rise if work is done by the gas.  (b) No. The only way that the temperature can rise is if heat is added to the gas.  (c) Yes. The temperature can rise if work is done on the gas. Section 15.8  Heat Engines

13. A heat engine takes heat QH from a hot reservoir and uses part of this energy to perform work W. Assuming that QH cannot be changed, how can the efficiency of the engine be improved?  (a) Increase the work W; the heat QC rejected to the cold reservoir increases as a result.  (b) Increase the work W; the heat QC rejected to the cold reservoir remains unchanged.  (c) Increase the work W; the heat QC rejected to the cold reservoir decreases as a result.  (d) Decrease the work W; the heat QC rejected to the cold reservoir remains unchanged.  (e) Decrease the work W; the heat QC rejected to the cold reservoir decreases as a result. Section 15.9  Carnot’s Principle and the Carnot Engine

15. The three Carnot engines shown in the drawing operate with hot and cold reservoirs whose temperature differences are 100 K. Rank the efficiencies of the engines, largest to smallest.  (a) All engines have the same efficiency.  (b) A, B, C  (c) B, A, C  (d) C, B, A  (e) C, A, B

Section 15.10  Refrigerators, Air Conditioners, and Heat Pumps 17. A refrigerator operates for a certain time, and the work done by the electrical energy during this time is W 5 1000 J. What can be said about the heat delivered to the room containing the refrigerator?  (a) The heat delivered to the room is less than 1000 J.  (b) The heat delivered to the room is equal to 1000 J.  (c) The heat delivered to the room is greater than 1000 J. Section 15.11  Entropy

19. Heat is transferred from the sun to the earth via electromagnetic waves (see Chapter 24). Because of this transfer, the entropy ofthe sun ________, the entropy of the earth ________, and the entropy of the sun–earth system ________.  (a) increases, decreases, decreases  (b) decreases, increases, increases  (c) increases, increases, increases  (d) increases, decreases, increases  (e) decreases, increases, decreases Problems

Section 15.4  Thermal Processes

13. The pressure and volume of a gas are changed along the path ABCA. Using...

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