Free Practice Quiz Question List

5 Thermodynamic Cycles and Devices Online Quiz Questions

Use this free practice quiz with 20 questions to review 5 Thermodynamic Cycles and Devices, test your knowledge, and prepare for your next test or exam.

20 questions

Choose one

1 point

A working substance completes a thermodynamic cycle and returns to its initial state. What is its net internal-energy change over the cycle?

A
Its net internal-energy change is positive because it absorbs heat.
B
Its net internal-energy change is zero because it returns to its initial state.
C
Its net internal-energy change equals the net work produced.
D
Its net internal-energy change is negative whenever the cycle produces work.

Choose one

1 point

A heat engine absorbs $900\,\text{J}$ of heat and rejects $550\,\text{J}$ during one cycle. How much net work does it produce per cycle?

A
200 J
B
550 J
C
350 J
D
1,450 J

Choose one

1 point

A refrigerator removes $720\,\text{J}$ of heat from its interior while receiving $240\,\text{J}$ of work. What is its coefficient of performance?

A
$3$
B
$0.33$
C
$2$
D
$4$

Choose all

1 point

Select all statements that are correct for a complete thermodynamic cycle using the convention that heat entering the substance and work done by it are positive.

A
The net heat transfer over a complete cycle equals the net work for that cycle.
B
The working substance must have a nonzero net internal-energy change if the cycle produces work.
C
The enclosed area on a pressure–volume diagram represents the net work for the cycle.
D
The enclosed area on a pressure–volume diagram represents the heat rejected only.

Choose all

1 point

Select all statements that correctly compare a refrigerator and a heat pump operating on the same reversed-cycle principle.

A
A refrigerator's COP uses heat removed from the cold region in its numerator.
B
A heat pump's COP uses heat removed from the cold region in its numerator.
C
A refrigerator and a heat pump operate without work input if they share the same cycle.
D
A heat pump's COP is one greater than the refrigerator's COP for the same device and operating conditions.

True or false

1 point

A cyclic heat engine operates between a hot and a cool reservoir. True or false: it can convert all the heat it absorbs into net work, provided energy is conserved.

A
True
B
False

True or false

1 point

True or false: A refrigerator with a COP greater than 1 violates energy conservation because it removes more heat than the work supplied to it.

A
True
B
False

Written response

1 point

An ideal reversible engine operates between a hot reservoir at $600\,\text{K}$ and a cold reservoir at $300\,\text{K}$ . What is its maximum Carnot efficiency as a decimal between 0 and 1?

Written response

1 point

In a vapor-compression cycle, what happens to the refrigerant vapor's pressure and temperature when it passes through the compressor? Enter a short phrase.

Fill in the blank

1 point

For a refrigerator, $\mathrm{COP}_{\text{R}}=$ , where $Q_C$ is heat removed from the cold region and $W_{\text{in}}$ is supplied work.

Fill in the blank

1 point

In a vapor-compression refrigerator, the releases heat to the warmer surroundings, while the absorbs heat from the refrigerated space.

Open ended

1 point

Explain how a refrigerator and a heat pump differ in the useful effect used to define their COPs. Use energy conservation to show how their COPs are related, and explain why a COP greater than 1 is not a thermal efficiency greater than 100%.

Choose one

1 point

An ideal reversible refrigerator operates between reservoirs at $270\,\text{K}$ and $330\,\text{K}$ . What is its maximum Carnot COP?

A
$0.22$
B
$4.5$
C
$5.5$
D
$6.0$

True or false

1 point

A reversible refrigerator keeps its cold reservoir temperature fixed while the warm reservoir becomes hotter. True or false: its maximum Carnot COP decreases.

A
True
B
False

Choose one

1 point

A working substance completes a thermodynamic cycle and returns to its initial state. Which statement must be true about its net internal-energy change over the cycle?

A
The working substance has gained internal energy because it has completed a cycle.
B
The working substance returns to its initial state, so its net internal-energy change is zero.
C
The working substance has lost internal energy equal to the net work.
D
The net internal-energy change depends on whether the cycle is clockwise.

Choose one

1 point

A device can be operated as either a refrigerator or a heat pump. Which choice correctly identifies the useful effect for each mode?

A
A refrigerator delivers heat to a warm space, while a heat pump removes heat from a cool space.
B
A refrigerator and a heat pump have different energy-conservation equations.
C
A refrigerator is judged by heat removed from a cool space, while a heat pump is judged by heat delivered to a warm space.
D
A refrigerator requires no work input, while a heat pump does.

Choose one

1 point

A heat engine absorbs $900\,\text{J}$ of heat and rejects $600\,\text{J}$ during each cycle. How much net work does it produce per cycle?

A
$300\,\text{J}$
B
$600\,\text{J}$
C
$900\,\text{J}$
D
$1500\,\text{J}$

Choose one

1 point

A cycle forms a clockwise loop on a pressure–volume diagram. Which interpretation is correct?

A
The enclosed area represents the net heat rejected, and a clockwise cycle requires work input.
B
The enclosed area represents the change in internal energy, and a clockwise cycle has a positive change.
C
The enclosed area represents the maximum possible efficiency, and direction does not matter.
D
The enclosed area represents net work, and a clockwise cycle generally produces net work.

Written response

1 point

In a vapor-compression refrigerator, what is the name of the component where the refrigerant absorbs heat from the refrigerated space and evaporates?

Written response

1 point

An ideal Carnot engine operates between reservoirs at $T_H=500\,\text{K}$ and $T_C=300\,\text{K}$ . What is its maximum efficiency as a decimal fraction?