Question 1

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 2

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 3

A heat engine performs the reversible cycle abca with 9.0 moles of an ideal gas,as shown in the figure.Path ca is an adiabatic process.The temperatures at points a and b are 300 K and 500 K,respectively.The volume at point c is 0.20 m3.The adiabatic constant of the gas is 1.60.The thermal efficiency of this engine is closest to

Accepted Answer

A) 0.070. 
B) 0.10. 
C) 0.13. 
D) 0.16. 
E) 0.19. 
A) 0.070. 
B) 0.10. 
C) 0.13. 
D) 0.16. 
E) 0.19.

Question 4

An ideal Carnot engine operates between reservoirs having temperatures of 125°C and
-20°C.Each cycle the heat expelled by this engine is used to melt 30.0 g of ice at 0.00°C.The heat of fusion of water is 3.34 × 105 J/kg and the heat of vaporization of water is
2.25 × 106 J/kg.
(a)How much work does this engine do each cycle?
(b)How much heat per cycle does this engine absorb at the hot reservoir?

Accepted Answer

(a)5740 J

Question 5

A Carnot engine operates between reservoirs at 550K and 300K,discarding 1500 J of heat in each cycle.
(a)What is the engine's efficiency?
(b)How much heat is supplied to the engine by the hot reservoir in each cycle?

Accepted Answer

The answer of A Carnot engine operates between reservoirs at...

Question 6

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 7

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 8

The compressor in a certain Carnot refrigerator performs 480 J of work to remove 150 J of heat from the interior of the refrigerator.How much heat must the coils behind the refrigerator discharge into the kitchen?

Accepted Answer

A) 110 J 
B) 150 J 
C) 330 J 
D) 480 J 
E) 630 J 
A) 110 J 
B) 150 J 
C) 330 J 
D) 480 J 
E) 630 J

Question 9

A brass rod,75.0 cm long and having a cross-sectional area of 2.50 cm2,conducts heat from a large furnace at 375°C into a very large cold water bath at 10.0°C without losing any heat at the lateral surface of the rod.Steady state has been established,and the thermal conductivity of brass is   .The rate at which the entropy of the system (furnace plus water)is changing is closest to

Accepted Answer

A) 2.05 × 10-2 W/K. 
B) 2.64 × 10-2 W/K. 
C) 3.54 × 10-2 W/K. 
D) 4.69 × 10-2 W/K. 
E) 6.74 × 10-2 W/K. 
A) 2.05 × 10-2 W/K. 
B) 2.64 × 10-2 W/K. 
C) 3.54 × 10-2 W/K. 
D) 4.69 × 10-2 W/K. 
E) 6.74 × 10-2 W/K.

Question 10

A certain Carnot heat pump transfers energy from the outside of a house,where the temperature is -15°C,to the inside of a room where the temperature is 21°C.If this heat pump runs off of electricity,what is the minimum rate at which it uses electrical energy to deliver
150 W to the inside room?

Accepted Answer

The answer of A certain Carnot heat pump transfers energy...

Question 11

A nuclear fission power plant has an actual efficiency of 39%.If   of power are produced by the nuclear fission,how much electric power does the power plant output?

Accepted Answer

A) 0.098 MW 
B) 9.8 MW 
C) 35 MW 
D) 0.35 MW 
A) 0.098 MW 
B) 9.8 MW 
C) 35 MW 
D) 0.35 MW

Question 12

An automobile engine takes in 4000 J of heat and performs 1100 J of mechanical work in each cycle.
(a)Calculate the engine's efficiency.
(b)How much heat is "wasted" in each cycle?

Accepted Answer

The answer of An automobile engine takes in 4000 J...

Question 13

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

Question 14

A refrigerator has a coefficient of performance equal to 4.2.How much work must be done on the refrigerator in order to remove 250 J of heat from the interior?

Accepted Answer

A) 60 J 
B) 120 J 
C) 250 J 
D) 480 J 
E) 1050 J 
A) 60 J 
B) 120 J 
C) 250 J 
D) 480 J 
E) 1050 J

Question 15

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 16

At atmospheric pressure,45 moles of liquid helium are vaporized at its boiling point of   The heat of vaporization of helium,at atmospheric pressure,is   and the atomic weight of helium is   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 17

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 18

An ideal reversible refrigerator keeps its inside compartment at 9.0°C.What is the high temperature,Th,needed to give this refrigerator a coefficient of performance of 3.7?

Accepted Answer

A) 85°C 
B) 1052°C 
C) 11°C 
D) 42°C 
A) 85°C 
B) 1052°C 
C) 11°C 
D) 42°C

Question 19

A Carnot air conditioner operates between an indoor temperature of 20°C and an outdoor temperature of 39°C.How much energy does it need to remove 2000 J of heat from the interior of the house?

Accepted Answer

A) 105 J 
B) 130 J 
C) 780 J 
D) 520 J 
E) 340 J 
A) 105 J 
B) 130 J 
C) 780 J 
D) 520 J 
E) 340 J

Question 20

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

Exam 21: Heat Engines and 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?

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?

A Carnot engine operates between reservoirs at 550K and 300K,discarding 1500 J of heat in each cycle. (a)What is the engine's efficiency? (b)How much heat is supplied to the engine by the hot reservoir in each cycle?

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?

The compressor in a certain Carnot refrigerator performs 480 J of work to remove 150 J of heat from the interior of the refrigerator.How much heat must the coils behind the refrigerator discharge into the kitchen?

A certain Carnot heat pump transfers energy from the outside of a house,where the temperature is -15°C,to the inside of a room where the temperature is 21°C.If this heat pump runs off of electricity,what is the minimum rate at which it uses electrical energy to deliver 150 W to the inside room?

A nuclear fission power plant has an actual efficiency of 39%.If of power are produced by the nuclear fission,how much electric power does the power plant output?

An automobile engine takes in 4000 J of heat and performs 1100 J of mechanical work in each cycle. (a)Calculate the engine's efficiency. (b)How much heat is "wasted" in each cycle?

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

A refrigerator has a coefficient of performance equal to 4.2.How much work must be done on the refrigerator in order to remove 250 J of heat from the interior?

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?

At atmospheric pressure,45 moles of liquid helium are vaporized at its boiling point of The heat of vaporization of helium,at atmospheric pressure,is and the atomic weight of helium is The change in the entropy of the helium,as it vaporizes,is closest to

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?

An ideal reversible refrigerator keeps its inside compartment at 9.0°C.What is the high temperature,Th,needed to give this refrigerator a coefficient of performance of 3.7?

A Carnot air conditioner operates between an indoor temperature of 20°C and an outdoor temperature of 39°C.How much energy does it need to remove 2000 J of heat from the interior of the house?

Concepts of Motion

Kinematics in One Dimension

Vectors and Coordinate Systems

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Force and Motion

Dynamics I: Motion Along a Line

Newtons Third Law

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Newtons Theory of Gravity

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Work, heat, and the First Law of Thermodynamics

The Micromacro Connection

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Gausss Law

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An ideal reversible refrigerator keeps its inside compartment at 9.0°C.What is the high temperature,T_h,needed to give this refrigerator a coefficient of performance of 3.7?