Question 1

Entropy: The second law of thermodynamics leads us to conclude that

Accepted Answer

A)  the total energy of the universe is constant. 
B)  disorder in the universe is increasing with the passage of time. 
C)  it is theoretically impossible to convert work into heat with 100% efficiency. 
D)  the total energy in the universe is increasing with time. 
E)  the total energy in the universe is decreasing with time. 
A)  the total energy of the universe is constant. 
B)  disorder in the universe is increasing with the passage of time. 
C)  it is theoretically impossible to convert work into heat with 100% efficiency. 
D)  the total energy in the universe is increasing with time. 
E)  the total energy in the universe is decreasing with time. B

Question 2

Entropy: A 2.0-kg block of aluminum at 50°C is dropped into 5.0 kg of water at 20°C and the temperature is allowed to stabilize. What is the total change in entropy during this process, assuming no heat is exchanged with the environment? The specific heat of aluminum is 910 J/(kg∙K) and the specific heat of water is 4190 J/(kg∙K).

Accepted Answer

A)  8.2 J/K 
B)  10 J/K 
C)  3.3 × 10-2 J/K 
D)  3.8 × 10-3 J/K 
E)  2.4 × 10-3 J/K 
A)  8.2 J/K 
B)  10 J/K 
C)  3.3 × 10-2 J/K 
D)  3.8 × 10-3 J/K 
E)  2.4 × 10-3 J/K A

Question 3

Heat engines: A heat engine with an efficiency of 30.0% performs 2500 J of work. How much heat is discharged to the lower temperature reservoir?

Accepted Answer

A)  5830 J 
B)  8330 J 
C)  750 J 
D)  1350 J 
E)  7080 J 
A)  5830 J 
B)  8330 J 
C)  750 J 
D)  1350 J 
E)  7080 J A

Question 4

Entropy: The entropy of an isolated system must be conserved, so it never changes.

Accepted Answer

A) True 
 B)False

Question 5

Entropy: A system consists of two very large thermal reservoirs in contact with each other, one at temperature 300°C and the other at temperature 200°C. When 600 J of heat transfers from the 300°C reservoir to the 200°C reservoir, what is the change in entropy of this system?

Accepted Answer

A)  0.221 J/K 
B)  1.00 J/K 
C)  5.00 J/K 
D)  -1.00 J/K 
E)  -2.31 J/K 
A)  0.221 J/K 
B)  1.00 J/K 
C)  5.00 J/K 
D)  -1.00 J/K 
E)  -2.31 J/K

Question 6

Refrigerators: During each cycle of operation, a refrigerator absorbs 230 J of heat from the freezer and expels 356 J of heat to the room. How much work input is required in each cycle?

Accepted Answer

A)  712 J 
B)  586 J 
C)  460 J 
D)  310 J 
E)  126 J 
A)  712 J 
B)  586 J 
C)  460 J 
D)  310 J 
E)  126 J

Question 7

Entropy: A 810-g quantity of ethanol, in the liquid state at its melting point of   is frozen at atmospheric pressure. The heat of fusion of ethanol is 1.04 × 105 J/kg, the molecular mass is 46.1 g/mol, and the ideal gas constant is R = 8.314 J/(mol∙K). The change in the entropy of the ethanol as it freezes is closest to

Accepted Answer

A)  -540 J/K. 
B)  -490 J/K. 
C)  -600 J/K. 
D)  490 J/K. 
E)  540 J/K. 
A)  -540 J/K. 
B)  -490 J/K. 
C)  -600 J/K. 
D)  490 J/K. 
E)  540 J/K.

Question 8

Refrigerators: A refrigerator has a coefficient of performance of 1.15, and it extracts 7.95 J of heat from the cold reservoir during each cycle.
(a) How much work is done on the gas in each cycle?
(b) How much heat is exhausted into the hot reservoir in each cycle?

Accepted Answer

(a) 6.91 J

Question 9

Entropy: What is the change in entropy of 10.0 moles of ideal monatomic gas that reversibly undergoes the isothermal expansion shown in the figure? The ideal gas constant is R = 8.314 J/(mol∙K).

Accepted Answer

A)  221 J/K 
B)  104 J/K 
C)  63.1 J/K 
D)  45.2 J/K 
E)  90.8 J/K 
A)  221 J/K 
B)  104 J/K 
C)  63.1 J/K 
D)  45.2 J/K 
E)  90.8 J/K

Question 10

Heat pumps: An air conditioner with a coefficient of performance of 3.5 uses 30 kW of power. How much power is it discharging to the outdoors?

Accepted Answer

A)  30 kW 
B)  75 kW 
C)  105 kW 
D)  135 kW 
E)  210 kW 
A)  30 kW 
B)  75 kW 
C)  105 kW 
D)  135 kW 
E)  210 kW

Question 11

Heat engines: A real (non-Carnot) heat engine, operating between heat reservoirs at temperatures of   and   performs 2.4 kJ of net work and rejects   of heat in a single cycle. The thermal efficiency of this heat engine is closest to

Accepted Answer

A)  0.21. 
B)  0.19. 
C)  0.17. 
D)  0.23. 
E)  0.25. 
A)  0.21. 
B)  0.19. 
C)  0.17. 
D)  0.23. 
E)  0.25.

Question 12

Refrigerators: A refrigerator removes heat from the freezing compartment at the rate of 20 kJ and ejects 24 kJ into a room per cycle. How much work is required in each cycle?

Accepted Answer

A)  4 kJ 
B)  20 kJ 
C)  22 kJ 
D)  24 kJ 
E)  44 kJ 
A)  4 kJ 
B)  20 kJ 
C)  22 kJ 
D)  24 kJ 
E)  44 kJ

Question 13

Entropy: At atmospheric pressure, 45 moles of liquid helium are vaporized at its boiling point of 4.22 K. The heat of vaporization of helium, at atmospheric pressure, is 2.09 × 104 J/kg, and the atomic weight of helium is 4.00 g/mol. The change in the entropy of the helium, as it vaporizes, is closest to

Accepted Answer

A)  890 J/K. 
B)  14,000 J/K. 
C)  18,000 J/K. 
D)  -9400 J/K. 
E)  -14,000 J/K. 
A)  890 J/K. 
B)  14,000 J/K. 
C)  18,000 J/K. 
D)  -9400 J/K. 
E)  -14,000 J/K.

Question 14

Heat engines: A heat engine takes 2.0 moles of an ideal gas through the reversible cycle abca, on the pV diagram shown in the figure. The path bc is an isothermal process. The temperature at c is 820 K, and the volumes at a and c are 0.010 m3 and 0.16 m3, respectively. The molar heat capacity at constant volume, of the gas, is 37 J/mol∙K, and the ideal gas constant is R = 8.314 J/(mol∙K). The thermal efficiency of the engine is closest to

Accepted Answer

A)  0.26. 
B)  0.026. 
C)  0.33. 
D)  0.40. 
E)  0.53. 
A)  0.26. 
B)  0.026. 
C)  0.33. 
D)  0.40. 
E)  0.53.

Question 15

Carnot devices: A Carnot refrigerator has a coefficient of performance of 2.5. The refrigerator consumes 50 W of power. How much heat is removed from the interior of the refrigerator in 1 hour?

Accepted Answer

A)  7.5 kJ 
B)  450 kJ 
C)  180 kJ 
D)  720 kJ 
E)  72 kJ 
A)  7.5 kJ 
B)  450 kJ 
C)  180 kJ 
D)  720 kJ 
E)  72 kJ

Question 16

Heat engines: Is it possible to transfer heat from a hot reservoir to a cold reservoir?

Accepted Answer

A)  No; this is forbidden by the second law of thermodynamics. 
B)  Yes; this will happen naturally. 
C)  Yes, but work will have to be done. 
D)  Theoretically yes, but it hasn't been accomplished yet. 
A)  No; this is forbidden by the second law of thermodynamics. 
B)  Yes; this will happen naturally. 
C)  Yes, but work will have to be done. 
D)  Theoretically yes, but it hasn't been accomplished yet.

Question 17

Entropy: A 2.00-kg block of ice at 0.00°C is dropped into a very large lake at 25.0°C and completely melts. For water, the heat of fusion is 3.35 × 105 J/kg, the heat of vaporization is 2.25 × 105 J/kg, and the specific heat is 4190 J/kg∙K. The net change in entropy of the system consisting of the ice and the lake due to this melting process is closest to

Accepted Answer

A)  2.45 × 103 J/K. 
B)  2.24 × 103 J/K. 
C)  2.06 × 102 J/K. 
D)  -2.45 × 103 J/K. 
E)  -2.06 × 102 J/K. 
A)  2.45 × 103 J/K. 
B)  2.24 × 103 J/K. 
C)  2.06 × 102 J/K. 
D)  -2.45 × 103 J/K. 
E)  -2.06 × 102 J/K.

Question 18

Carnot engine: A Carnot cycle engine operates between a low temperature reservoir at 20°C and a high temperature reservoir at 800°C. If the engine is required to output 20.0 kJ of work per cycle, how much heat must the high temperature reservoir transfer to the engine during each cycle?

Accepted Answer

A)  27.5 kJ 
B)  73.2 kJ 
C)  39.2 kJ 
D)  800 kJ 
E)  20.5 kJ 
A)  27.5 kJ 
B)  73.2 kJ 
C)  39.2 kJ 
D)  800 kJ 
E)  20.5 kJ

Question 19

Carnot engine: A Carnot engine operates between a high temperature reservoir at   and a river with water at   If it absorbs   of heat each cycle, how much work per cycle does it perform?

Accepted Answer

A)  1318 J 
B)  2382 J 
C)  1449 J 
D)  2251 J 
A)  1318 J 
B)  2382 J 
C)  1449 J 
D)  2251 J

Question 20

Carnot engine: A coal-fired plant generates 600 MW of electric power. The plant uses 4.8 × 106 kg of coal each day. The heat produced by the combustion of coal is 3.3 × 107 J/kg. The steam that drives the turbines is at a temperature of 300°C, and the exhaust water is at 37°C.
(a) What is the overall efficiency of the plant for generating electric power?
(b) What is the maximum efficiency that this plant could possibly have using the same temperature extremes that it presently uses?
(c) How much thermal energy is exhausted each day by this plant?

Accepted Answer

(a) 33% 
(

Exam 15: Mechanical Waves

Entropy: The second law of thermodynamics leads us to conclude that

Heat engines: A heat engine with an efficiency of 30.0% performs 2500 J of work. How much heat is discharged to the lower temperature reservoir?

Entropy: The entropy of an isolated system must be conserved, so it never changes.

Entropy: A system consists of two very large thermal reservoirs in contact with each other, one at temperature 300°C and the other at temperature 200°C. When 600 J of heat transfers from the 300°C reservoir to the 200°C reservoir, what is the change in entropy of this system?

Refrigerators: During each cycle of operation, a refrigerator absorbs 230 J of heat from the freezer and expels 356 J of heat to the room. How much work input is required in each cycle?

Refrigerators: A refrigerator has a coefficient of performance of 1.15, and it extracts 7.95 J of heat from the cold reservoir during each cycle. (a) How much work is done on the gas in each cycle? (b) How much heat is exhausted into the hot reservoir in each cycle?

Entropy: What is the change in entropy of 10.0 moles of ideal monatomic gas that reversibly undergoes the isothermal expansion shown in the figure? The ideal gas constant is R = 8.314 J/(mol∙K).

Heat pumps: An air conditioner with a coefficient of performance of 3.5 uses 30 kW of power. How much power is it discharging to the outdoors?

Heat engines: A real (non-Carnot) heat engine, operating between heat reservoirs at temperatures of and performs 2.4 kJ of net work and rejects of heat in a single cycle. The thermal efficiency of this heat engine is closest to

Refrigerators: A refrigerator removes heat from the freezing compartment at the rate of 20 kJ and ejects 24 kJ into a room per cycle. How much work is required in each cycle?

Carnot devices: A Carnot refrigerator has a coefficient of performance of 2.5. The refrigerator consumes 50 W of power. How much heat is removed from the interior of the refrigerator in 1 hour?

Heat engines: Is it possible to transfer heat from a hot reservoir to a cold reservoir?

Carnot engine: A Carnot cycle engine operates between a low temperature reservoir at 20°C and a high temperature reservoir at 800°C. If the engine is required to output 20.0 kJ of work per cycle, how much heat must the high temperature reservoir transfer to the engine during each cycle?

Carnot engine: A Carnot engine operates between a high temperature reservoir at and a river with water at If it absorbs of heat each cycle, how much work per cycle does it perform?

Motion Along a Straight Line

Motion in Two or Three Dimensions

Newtons Laws of Motion

Applying Newtons Laws

Work and Kinetic Energy

Potential Energy and Energy Conservation

Momentum, Impulse, and Collisions

Rotation of Rigid Bodies

Dynamics of Rotational Motion

Equilibrium and Elasticity

Fluid Mechanics

Gravitation

Periodic Motion

Sound and Hearing

Temperature and Heat

Thermal Properties of Matter

The First Law of Thermodynamics

The Second Law of Thermodynamics

Electric Charge and Electric Field

Gausss Law

Electric Potential

Capacitance and Dielectrics

Current, Resistance, and Electromotive Force

Direct-Current Circuits

Magnetic Field and Magnetic Forces

Sources of Magnetic Field

Electromagnetic Induction

Inductance

Alternating Current

Electromagnetic Waves Optics

The Nature and Propagation of Light

Geometric Optics

Interference

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