PV Diagram Quiz: Test Your Knowledge Of Thermodynamic Cycles

Grade 10th

Reviewed by Ekaterina Yukhnovich

Ekaterina Yukhnovich, PhD |

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Ekaterina V. is a physicist and mathematics expert with a PhD in Physics and Mathematics and extensive experience working with advanced secondary and undergraduate-level content. She specializes in combinatorics, applied mathematics, and scientific writing, with a strong focus on accuracy and academic rigor.

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By Thames

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Quizzes Created: 11119 | Total Attempts: 9,762,531

| Attempts: 16 | Questions: 20 | Updated: Mar 13, 2026

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1. Returning to the starting point on a pv diagram implies the internal energy change over the cycle is zero.

True

False

Concept: state function over a cycle. Internal energy depends only on state, not path. Since the state returns to the start, (\delta u = 0) over the full cycle.

Explanation

Concept: state function over a cycle. Internal energy depends only on state, not path. Since the state returns to the start, (\delta u = 0) over the full cycle.

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About This Quiz

Pv Diagram Quiz: Test Your Knowledge Of Thermodynamic Cycles - Quiz

This assessment delves into PV diagrams and thermodynamic cycles, evaluating your understanding of key concepts such as work, heat, and efficiency. By testing your knowledge, it helps reinforce critical skills necessary for mastering thermodynamics, making it valuable for students and professionals alike.

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2. A pv diagram is especially useful for comparing different engine cycle designs qualitatively.

True

False

Concept: visual comparison tool. pv diagrams let you see expansions, compressions, and net work at a glance. They’re a standard way to compare cycle shapes and expected work output.

Explanation

Concept: visual comparison tool. pv diagrams let you see expansions, compressions, and net work at a glance. They’re a standard way to compare cycle shapes and expected work output.

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3. Real engine cycles differ from ideal pv cycles because of friction, heat loss, and non-equilibrium effects.

True

False

Concept: real vs ideal cycles. Ideal cycles assume perfectly controlled steps and no losses. Real engines have irreversibility that changes the pv loop and reduces work output.

Explanation

Concept: real vs ideal cycles. Ideal cycles assume perfectly controlled steps and no losses. Real engines have irreversibility that changes the pv loop and reduces work output.

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4. A cycle that runs counterclockwise on a pv diagram typically corresponds to:

Positive net work produced by the gas

Net work input required (refrigerator/heat pump)

Zero heat transfer

No pressure changes

Concept: work sign via loop direction. Counterclockwise loops mean the surroundings do net work on the gas. That matches refrigeration cycles requiring electrical input.

Explanation

Concept: work sign via loop direction. Counterclockwise loops mean the surroundings do net work on the gas. That matches refrigeration cycles requiring electrical input.

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5. Which describes an 'isothermal' process?

Constant volume

Constant pressure

Constant temperature

Constant mass only

Concept: isothermal meaning. Isothermal means temperature stays constant during the process. It’s an idealisation used in some cycle models.

Explanation

Concept: isothermal meaning. Isothermal means temperature stays constant during the process. It’s an idealisation used in some cycle models.

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6. In many cycles, heat is added mainly during:

The coldest part of the cycle only

High-temperature portions of the cycle

Only during compression

Only when pressure is zero

Concept: heat addition at high t. Adding heat at higher temperatures can improve theoretical efficiency. Many ideal cycles arrange heat input to happen at higher temperature stages.

Explanation

Concept: heat addition at high t. Adding heat at higher temperatures can improve theoretical efficiency. Many ideal cycles arrange heat input to happen at higher temperature stages.

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7. Which step is 'constant volume' on a pv diagram?

A horizontal line

A vertical line

A circle

A diagonal line with slope 1

Concept: isochoric process. Volume is fixed on a vertical line. Pressure can change while volume stays constant.

Explanation

Concept: isochoric process. Volume is fixed on a vertical line. Pressure can change while volume stays constant.

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8. The net work output of an engine cycle increases if:

The loop area decreases

The loop area increases

The loop becomes a straight line

Pressure becomes zero everywhere

Concept: work equals area. Larger enclosed pv area corresponds to more net work per cycle. This is a qualitative design goal for many engine cycles.

Explanation

Concept: work equals area. Larger enclosed pv area corresponds to more net work per cycle. This is a qualitative design goal for many engine cycles.

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9. During an expansion step, the gas volume:

Decreases

Increases

Stays constant

Becomes negative

Concept: expansion vs compression. Expansion means the gas takes up more volume. Engines often produce work during expansion.

Explanation

Concept: expansion vs compression. Expansion means the gas takes up more volume. Engines often produce work during expansion.

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10. If the pv loop is clockwise, the cycle typically represents:

A refrigerator consuming work

A heat engine producing net work

No net work

A process with zero heat transfer

Concept: loop direction. Clockwise cycles generally indicate the gas does positive net work on the surroundings. Counterclockwise loops usually indicate work input (refrigerator/heat pump).

Explanation

Concept: loop direction. Clockwise cycles generally indicate the gas does positive net work on the surroundings. Counterclockwise loops usually indicate work input (refrigerator/heat pump).

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11. For a complete cycle on a pv diagram, the net work done is the area enclosed by the loop.

True

False

Concept: cycle work as enclosed area. A full cycle returns to the starting state, so the net work equals the enclosed loop area. The direction of the loop indicates whether the system produces work or consumes work.

Explanation

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12. A constant pressure process appears as a horizontal line on a pv diagram.

True

False

Concept: isobaric process. Pressure is fixed along a horizontal line. Volume changes while pressure remains the same.

Explanation

Concept: isobaric process. Pressure is fixed along a horizontal line. Volume changes while pressure remains the same.

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13. Compression steps often require work input to the gas.

True

False

Concept: work sign. Compressing a gas typically means pushing on it, transferring work into the gas. In cycles, some steps require work while others deliver work.

Explanation

Concept: work sign. Compressing a gas typically means pushing on it, transferring work into the gas. In cycles, some steps require work while others deliver work.

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14. On a pressure–volume (pv) diagram, the work done by a gas during a process is related to:

The slope only

The area under the curve

The colour of the curve

The time taken only

Concept: work on pv graphs. For a gas process, (w) corresponds to the integral of (p,dv), which is the area under the curve. This is why pv plots are so useful for engines.

Explanation

Concept: work on pv graphs. For a gas process, (w) corresponds to the integral of (p,dv), which is the area under the curve. This is why pv plots are so useful for engines.

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15. For a full cycle, the first law implies:

(q_{in} = 0)

(w = 0)

Net heat in equals net work out

Entropy must decrease

Concept: first law for cycles. Over a cycle, (\delta u = 0), so (q_{net} = w_{net}). Net heat added equals net work delivered.

Explanation

Concept: first law for cycles. Over a cycle, (\delta u = 0), so (q_{net} = w_{net}). Net heat added equals net work delivered.

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16. The pv diagram alone can show work, but it doesn’t directly show heat transfer on each step without extra information.

True

False

Concept: pv shows work, not heat directly. Work is linked to (p,dv) and thus pv area. Heat depends on the path and internal energy changes, so it needs thermodynamic information beyond just geometry.

Explanation

Concept: pv shows work, not heat directly. Work is linked to (p,dv) and thus pv area. Heat depends on the path and internal energy changes, so it needs thermodynamic information beyond just geometry.

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17. If an engine produces more work per cycle but absorbs the same (q_{in}), its efficiency:

Decreases

Increases

Stays the same

Becomes impossible

Concept: efficiency definition. Efficiency is (w/q_{in}). Increasing (w) while keeping (q_{in}) fixed increases efficiency.

Explanation

Concept: efficiency definition. Efficiency is (w/q_{in}). Increasing (w) while keeping (q_{in}) fixed increases efficiency.

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18. Which is a correct qualitative statement?

Bigger pv loop area always means lower efficiency

Bigger pv loop area usually means more work per cycle

Pv loop area equals temperature

Pv loop area equals entropy

Concept: work per cycle. The pv loop area corresponds to net work. Efficiency depends on both work and heat input, but area is directly tied to work.

Explanation

Concept: work per cycle. The pv loop area corresponds to net work. Efficiency depends on both work and heat input, but area is directly tied to work.

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19. A closed loop on a pv diagram indicates a ______ process.

Concept: cycles return to the start. In a cycle, the system returns to its initial state. That’s why state variables (like (p, v, t)) end where they began.

Explanation

Concept: cycles return to the start. In a cycle, the system returns to its initial state. That’s why state variables (like (p, v, t)) end where they began.

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