Question 1

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? A) 85°C B) 1052°C C) 11°C D) 42°C

Accepted Answer

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

Question 2

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?
A) The heat exhausted must always be greater than the work done according to the second law of thermodynamics.
B) This engine violates the first law of thermodynamics because 100 J + 20 J ≠ 80 J.
C) An engine would operate by taking in heat at the lower temperature and exhausting heat at the higher temperature.
D) The efficiency of this engine is greater than the ideal Carnot cycle efficiency.
E) There is nothing wrong with this claim because 100 J = 20 J + 80 J.

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 3

An ideal gas initially at 300 K and occupying a volume of 20 L is adiabatically compressed.If its final temperature is 400 K and γ = 1.30,what is its final volume?
A) 7.7 L
B) 14 L
C) 22 L
D) 52 L

Accepted Answer

For an adiabatic process, the relation between temperature and volume is given by $T_1V_1^{\gamma-1} = T_2V_2^{\gamma-1}$, where $T_1$ and $T_2$ are the initial and final temperatures, $V_1$ and $V_2$ are the initial and final volumes, and $\gamma$ is the heat capacity ratio. Rearranging for $V_2$, and substituting the given values ($T_1 = 300 K$, $T_2 = 400 K$, $V_1 = 20 L$, $\gamma = 1.30$), we can solve for $V_2$, which results in approximately 7.7 L.

Question 4

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

Accepted Answer

The statement is false. While the total entropy of an isolated system may remain constant, the entropy of individual subsystems within the system can still change. Additionally, the second law of thermodynamics states that the total entropy of a closed system tends to increase over time, so in reality, entropy is not conserved.

Question 5

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

Accepted Answer

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

Question 6

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 7

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) The entropy lost by the iron is equal to the entropy gained by the ocean.
B) The entropy gained by the iron is equal to the entropy lost by the ocean.
C) The change in the entropy of the iron-ocean system is zero.
D) The ocean gains more entropy than the iron loses.
E) The ocean gains less entropy than the iron loses.

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 8

As a result of any natural process,the total entropy of any system plus that of its environment
A) never decreases.
B) sometimes decreases.
C) never increases.
D) always stays the same.

Accepted Answer

The Second Law of Thermodynamics states that the total entropy of an isolated system always increases over time or remains constant, but never decreases. Since any real-world system is never truly isolated and always interacts with its environment, the total entropy of the system plus the environment will also never decrease.

Question 9

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) The entropy gained by the ice cube is equal to the entropy lost by the water.
B) The entropy lost by the ice cube is equal to the entropy gained by the water.
C) The net entropy change of the system (ice plus water) is zero because no heat was added to the system.
D) The entropy of the system (ice plus water) increases because the process is irreversible.
E) The entropy of the water does not change because its temperature did not change.

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 10

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

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 11

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
A) 0.35.
B) 0.31.
C) 0.28.
D) 0.38.
E) 0.42.

Accepted Answer

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

Question 12

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 13

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

Accepted Answer

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

Question 14

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?
A) 46%
B) 54%
C) 86%
D) 27%
E) 13%

Accepted Answer

The answer of A certain engine extracts 1300 J of...

Question 15

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

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 16

An ideal gas is allowed to expand slowly at constant temperature to twice its original volume. During the expansion,the gas absorbs 200 kJ of heat.
(a)What is the change in the internal (thermal)energy of the gas during the expansion?
(b)How much work does the gas do during the expansion?

Accepted Answer

The answer of An ideal gas is allowed to expand...

Question 17

The second law of thermodynamics leads us to conclude that
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.

Accepted Answer

The second law of thermodynamics states that the entropy (disorder) of a closed system increases over time. This means that disorder in the universe is increasing with the passage of time, which is option B. Option A is incorrect because the first law of thermodynamics states that energy is conserved, not necessarily constant. Option C is correct because the second law also states that it is impossible to achieve 100% efficiency in converting work into heat. Option D is incorrect because the total energy in the universe is actually constant, but it is constantly being redistributed and transformed. Option E is also incorrect because the total energy in the universe is not decreasing.

Question 18

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

Accepted Answer

According to the second law of thermodynamics, heat energy will naturally flow from a hot reservoir to a cold reservoir, but not in the reverse direction (i.e. from a cold reservoir to a hot reservoir) without the input of work. This means that it is possible to transfer heat from a cold reservoir to a hot reservoir, but only if work is done on the system to achieve this.

Question 19

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

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 20

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

Accepted Answer

The answer of During each cycle of operation,a refrigerator absorbs...

Quiz 1: A: Foundations

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?

An ideal gas initially at 300 K and occupying a volume of 20 L is adiabatically compressed.If its final temperature is 400 K and γ = 1.30,what is its final volume?

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

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 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 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.)

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

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 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 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

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

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

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?

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 ideal gas is allowed to expand slowly at constant temperature to twice its original volume. During the expansion,the gas absorbs 200 kJ of heat. (a)What is the change in the internal (thermal)energy of the gas during the expansion? (b)How much work does the gas do during the expansion?

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

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?

Quiz 1: A: Foundations

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?

An ideal gas initially at 300 K and occupying a volume of 20 L is adiabatically compressed.If its final temperature is 400 K and γ = 1.30,what is its final volume?

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

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 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 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.)

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

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 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 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

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

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

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?

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 ideal gas is allowed to expand slowly at constant temperature to twice its original volume. During the expansion,the gas absorbs 200 kJ of heat. (a)What is the change in the internal (thermal)energy of the gas during the expansion? (b)How much work does the gas do during the expansion?

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

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 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?