Honors Physics I chapter 10: Thermodynamics 2013-2014 Exam Multiple Choice



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Honors Physics I - Chapter 10: Thermodynamics 2013-2014 Exam
Multiple Choice

Identify the choice that best completes the statement or answers the question.

1. An ideal gas system is maintained at a constant volume of 4 L. If the pressure is constant, how much work is done by the system?

a.

0 J

b.

5 J

c.

8 J

d.

30 J

2. Which thermodynamic process takes place at a constant temperature so that the internal energy of a system remains unchanged?



a.

isovolumetric

b.

isobaric

c.

adiabatic

d.

isothermal

3. How is conservation of internal energy expressed for a system during an isothermal process?



a.

Q = W = 0, so DU = 0 and U = U

b.

Q = 0, so DU = –W

c.

DT = 0, so DU = 0; therefore, DU = QW = 0, or Q = W

d.

DV = 0, so PDV = 0 and W = 0; therefore, DU = Q

4. An ideal gas system undergoes an adiabatic process in which it expands and does 20 J of work on its environment. How much energy is transferred to the system as heat?



a.

–20 J

b.

0 J

c.

5 J

d.

20 J

5. How does a real heat engine differ from an ideal cyclic heat engine?



a.

A real heat engine is not cyclic.

b.

An ideal heat engine converts all energy from heat to work.

c.

A real heat engine is not isolated, so matter enters and leaves the engine.

d.

An ideal heat engine is not isolated, so matter enters and leaves the engine.

6. Which of the following is a way to improve the efficiency of a heat engine?



a.

increase Q

b.

reduce Q

c.

reduce W

d.

increase Q

7. How much work is done by 0.020 m3 of gas if its pressure increases by 2.0 ´ 105 Pa and the volume remains constant?



a.

0 J

b.

-4.0 ´ 103 J

c.

4.0 ´ 103 J

d.

1.0 ´ 107 J

8. A volume of cool air rapidly descends from the top of a mountain. The air is a poor thermal conductor, but its temperature increases as its volume decreases, because of the increase in atmospheric pressure as it reaches the ground. What thermodynamic process takes place?



a.

adiabatic

b.

isovolumetric

c.

isobaric

d.

isothermal

9. Which of the following statements about ideal cyclic processes is correct?



a.

The energy added as heat is converted entirely to work.

b.

The net work is greater than the net transfer of energy as heat.

c.

The net work done equals the net transfer of energy as heat.

d.

The net work is less than the net transfer of energy as heat.

10. A refrigerator removes a quantity of energy as heat from inside the refrigerator and transfers this energy to the air outside the refrigerator. Which statement correctly describes how this is done?



a.

Work is done on the system, so that energy can be transferred as heat from a low temperature to a high temperature.

b.

Work is done by the system, so that energy can be transferred as heat from a low temperature to a high temperature.

c.

Energy is transferred as heat spontaneously from the high temperature inside the refrigerator to the low temperature outside.

d.

Energy is transferred as heat spontaneously from the low temperature inside the refrigerator to the high temperature outside.

11. Which of the following situations would cause an ideal heat engine to do more work and still perform a cyclic process?



a.

increase the heat from the high-temperature reservoir

b.

decrease the heat from the high-temperature reservoir

c.

increase the heat removed to the low-temperature reservoir

d.

prevent any heat from being removed to the low-temperature reservoir

12. If two-thirds of the energy added to an engine as heat is removed to the engine’s surroundings as heat, what is the efficiency of the engine?



a.

1

b.

2/3

c.

1/2

d.

1/3

13. Work was done to freeze 1 kg of water. Which statement best describes what happened to this system?



a.

Its entropy increased.

b.

Its entropy remained constant.

c.

Its entropy decreased.

d.

Freezing occurred spontaneously.

14. What must be true of the combined entropy of a system and its environment?



a.

It increases.

b.

It remains constant.

c.

It decreases.

d.

It decreases at first, then increases.

15. An ideal gas system is maintained at a constant volume of 4 L. If the pressure is constant, how much work is done by the system?



a.

0 J

b.

5 J

c.

8 J

d.

30 J

16. Which thermodynamic process takes place at a constant temperature so that the internal energy of a system remains unchanged?



a.

isovolumetric

b.

isobaric

c.

adiabatic

d.

isothermal

17. An ideal gas system undergoes an adiabatic process in which it expands and does 20 J of work on its environment. What is the change in the system’s internal energy?



a.

-20 J

b.

-5 J

c.

0 J

d.

20 J

18. What occurs when a system’s disorder is increased?



a.

No work is done.

b.

No energy is available to do work.

c.

Less energy is available to do work.

d.

More energy is available to do work.

19. In an isovolumetric process for an ideal gas, the system’s change in the energy as heat is equivalent to a change in which of the following?



a.

temperature

b.

volume

c.

pressure

d.

internal energy

20. An ideal gas system undergoes an isovolumetric process in which 20 J of energy is added as heat to the gas. What is the change in the system’s internal energy?



a.

-20 J

b.

0 J

c.

5 J

d.

20 J

21. Which of the following is not a way in which a cyclic process resembles an isothermal process?



a.

Energy can be transferred as work.

b.

Energy can be transferred as heat.

c.

The temperature of the system remains constant throughout the process.

d.

There is no net change in the internal energy of the system.

22. An electrical power plant manages to transfer 88 percent of the heat produced in the burning of fossil fuel to convert water to steam. Of the heat carried by the steam, 40 percent is converted to the mechanical energy of the spinning turbine. Which best describes the overall efficiency of the heat-to-work conversion in the plant?



a.

greater than 88 percent

b.

88 percent

c.

40 percent

d.

less than 40 percent




Short Answer

1. What is true of the internal energy of an isolated system?
2. How does Qc 0 relate to the second law of thermodynamics?
3. A physics textbook is balanced on top of an inflated balloon on a cold morning. As the day passes, the temperature increases, the balloon expands, and the textbook rises. Is there a transfer of energy as heat? If so, what is it? Has any work been done? If so, on what?

Problem

1. The piston and flywheel part of a steam engine takes in 993 J of energy as heat and expels 514 J of energy as heat. The internal energy of the system increases by 372 J during the process. Work is done by steam at a pressure of 2.21 ´ 10 Pa. If the radius of the piston is 4.14 ´ 10 m, how far is the piston displaced?
2. A steam engine takes in 2.54 ´ 10 J of energy added as heat and exhausts 1.75 ´ 10 J of energy removed as heat per cycle. What is its efficiency?
3. The gas within a cylinder of an engine undergoes a net change in volume of 1.40 ´ 10 m when it does work at a constant pressure of 3.56 ´ 10 Pa. If the efficiency of the engine is 0.278, how much work must the engine give up as heat to the low-temperature reservoir?
4. A total of 165 J of work is done on a gaseous refrigerant as it undergoes compression. If the internal energy of the gas increases by 123 J during the process, what is the total amount of energy transferred as heat?
5. Over several cycles, a refrigerator compressor does work on the refrigerant. This work is equivalent to a constant pressure of 4.13 3 105 Pa compressing a circular piston with a radius of 0.019 m a distance of 25.0 m. If the change in the refrigerant’s internal energy is 0 J after each cycle, how much heat will the refrigerant remove from within the refrigerator

?



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