Question 1

A certain engine extracts 1300 J of heat from a hot temperature reservoir and discharges 700 J of heat to a cold temperature reservoir.What is the efficiency of this engine?

Accepted Answer

A

Question 2

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

E

Question 3

An ice cube at 0°C is placed in a very large bathtub filled with water at 30°C and allowed to melt,causing no appreciable change in the temperature of the bath water.Which one of the following statements is true?

Accepted Answer

The process of melting ice into water is irreversible, and in such processes, the total entropy of the system always increases. This is because the heat transfer from the warmer water to the colder ice cube increases the disorder of the system.

Question 4

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

The coefficient of performance (COP) for a refrigerator is defined as the ratio of the heat removed from the interior (Q_c) to the work done on the refrigerator (W), COP = Q_c / W. Given COP = 4.2 and Q_c = 250 J, we can rearrange the formula to solve for W: W = Q_c / COP = 250 J / 4.2 ≈ 60 J.

Question 5

A real (non-Carnot)heat engine,operating between heat reservoirs at temperatures of 650 K and 270 K,performs 4.3 kJ of net work and rejects 8.0 kJ of heat in a single cycle.The thermal efficiency of this heat engine is closest to

Accepted Answer

The answer of A real (non-Carnot)heat engine,operating between heat reservoirs...

Question 6

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?

Accepted Answer

The answer of An ideal reversible refrigerator keeps its inside...

Question 7

An engine manufacturer makes the claim that the engine they have developed will,on each cycle,take 100 J of heat out of boiling water at 100°C,do mechanical work of 80 J,and exhaust 20 J of heat at 10°C.What,if anything,is wrong with this claim?

Accepted Answer

The efficiency of a Carnot engine, which is the most efficient engine possible operating between two temperatures, is given by 1 - Tc/Th, where Tc is the cold reservoir temperature and Th is the hot reservoir temperature (in Kelvin). The efficiency claimed by the engine manufacturer exceeds this theoretical maximum, as it implies an efficiency of 80/100 = 80%, which is not possible between the given temperatures.

Question 8

According to the second law of thermodynamics,the entropy of any system always increases.

Accepted Answer

The second law of thermodynamics states that the total entropy of an isolated system can never decrease over time, and is constant if and only if all processes are reversible. However, in a non-isolated system, entropy can decrease.

Question 9

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

The work required in each cycle is the difference between the heat ejected into the room and the heat removed from the freezing compartment, which is 24 kJ - 20 kJ = 4 kJ.

Question 10

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 11

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

The answer of A refrigerator has a coefficient of performance...

Question 12

As a result of any natural process,the total entropy of any system plus that of its environment

Accepted Answer

The Second Law of Thermodynamics states that the total entropy of a closed system can never decrease, which means the total entropy of any system plus that of its environment can also never decrease. In fact, it tends to increase over time, leading to the concept of heat death or thermodynamic equilibrium.

Question 13

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

The answer of An air conditioner with a coefficient of...

Question 14

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

Accepted Answer

The statement is false. The second law of thermodynamics states that the total entropy of an isolated system tends to increase over time, leading to a state of maximum entropy or disorder. Entropy can only be conserved in reversible processes or in closed systems where there is no exchange of energy or matter with the surroundings.

Question 15

The second law of thermodynamics leads us to conclude that

Accepted Answer

The second law of thermodynamics is often called the law of increasing entropy, which states that the entropy (measure of disorder) of a closed system always tends to increase over time. In other words, the disorder in the universe is increasing with the passage of time. This is the reason why we cannot have perpetual motion machines and why we can never achieve 100% efficiency in converting work into heat. Additionally, the second law of thermodynamics does not address the total energy of the universe or whether it is constant or changing over time.

Question 16

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

Accepted Answer

It is possible to transfer heat from a cold reservoir to a hot reservoir, but work will have to be done. This requires the use of a heat pump or refrigerator, which uses work to move heat from a cold reservoir to a hot reservoir. This process does not violate the second law of thermodynamics because it requires the input of external work.

Question 17

A hot piece of iron is thrown into the ocean and its temperature eventually stabilizes.Which of the following statements concerning this process is correct? (There may be more than one correct choice.)

Accepted Answer

The ocean gains more entropy than the iron loses because when heat is transferred from a hotter object (the iron) to a colder one (the ocean), the increase in entropy of the colder object is greater than the decrease in entropy of the hotter object. This is due to the fact that entropy change is related to the amount of heat transferred divided by the temperature at which the transfer occurs, and the ocean's larger mass and lower temperature mean it can absorb heat with a greater increase in entropy.

Question 18

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

The efficiency of a heat engine is given by the ratio of work output to heat input, which can be expressed as $ \eta = \frac{W}{Q_{\text{in}}} $, where $ \eta $ is the efficiency, $ W $ is the work done by the engine, and $ Q_{\text{in}} $ is the heat input. Given an efficiency of 30.0% (or 0.30 when expressed as a decimal) and a work output of 2500 J, we can rearrange the formula to solve for $ Q_{\text{in}} $: $ Q_{\text{in}} = \frac{W}{\eta} = \frac{2500 \, \text{J}}{0.30} = 8333.33 \, \text{J} $. The heat discharged to the lower temperature reservoir is the difference between the heat input and the work output, which is $ Q_{\text{in}} - W = 8333.33 \, \text{J} - 2500 \, \text{J} = 5833.33 \, \text{J} $. The closest answer to this calculation is 5830 J.

Question 19

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

Accepted Answer

The answer of Is it possible to transfer heat from...

Question 20

A nuclear fission power plant has an actual efficiency of 39%.If 0.25 MW of power are produced by the nuclear fission,how much electric power does the power plant output?

Accepted Answer

The answer of A nuclear fission power plant has an...

Quiz 21: Degradation of Energy

A certain engine extracts 1300 J of heat from a hot temperature reservoir and discharges 700 J of heat to a cold temperature reservoir.What is the efficiency of this engine?

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?

An ice cube at 0°C is placed in a very large bathtub filled with water at 30°C and allowed to melt,causing no appreciable change in the temperature of the bath water.Which one of the following statements is true?

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?

A real (non-Carnot) heat engine,operating between heat reservoirs at temperatures of 650 K and 270 K,performs 4.3 kJ of net work and rejects 8.0 kJ of heat in a single cycle.The thermal efficiency of this heat engine is closest to

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?

An engine manufacturer makes the claim that the engine they have developed will,on each cycle,take 100 J of heat out of boiling water at 100°C,do mechanical work of 80 J,and exhaust 20 J of heat at 10°C.What,if anything,is wrong with this claim?

According to the second law of thermodynamics,the entropy of any system always increases.

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?

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 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?

As a result of any natural process,the total entropy of any system plus that of its environment

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?

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

The second law of thermodynamics leads us to conclude that

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

A hot piece of iron is thrown into the ocean and its temperature eventually stabilizes.Which of the following statements concerning this process is correct? (There may be more than one correct choice.)

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

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

A nuclear fission power plant has an actual efficiency of 39%.If 0.25 MW of power are produced by the nuclear fission,how much electric power does the power plant output?

Quiz 21: Degradation of Energy

A certain engine extracts 1300 J of heat from a hot temperature reservoir and discharges 700 J of heat to a cold temperature reservoir.What is the efficiency of this engine?

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?

An ice cube at 0°C is placed in a very large bathtub filled with water at 30°C and allowed to melt,causing no appreciable change in the temperature of the bath water.Which one of the following statements is true?

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?

A real (non-Carnot) heat engine,operating between heat reservoirs at temperatures of 650 K and 270 K,performs 4.3 kJ of net work and rejects 8.0 kJ of heat in a single cycle.The thermal efficiency of this heat engine is closest to

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?

An engine manufacturer makes the claim that the engine they have developed will,on each cycle,take 100 J of heat out of boiling water at 100°C,do mechanical work of 80 J,and exhaust 20 J of heat at 10°C.What,if anything,is wrong with this claim?

According to the second law of thermodynamics,the entropy of any system always increases.

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?

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 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?

As a result of any natural process,the total entropy of any system plus that of its environment

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?

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

The second law of thermodynamics leads us to conclude that

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

A hot piece of iron is thrown into the ocean and its temperature eventually stabilizes.Which of the following statements concerning this process is correct? (There may be more than one correct choice.)

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

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

A nuclear fission power plant has an actual efficiency of 39%.If 0.25 MW of power are produced by the nuclear fission,how much electric power does the power plant output?

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?