Master Thermodynamics: A Comprehensive Guide for Mechanical Engineering Students

Question 1

In a closed system undergoing a reversible isothermal process, what happens to the system's entropy?

Accepted Answer

Entropy remains constant.

Answer

Entropy increases.

Answer

Entropy decreases.

Answer

Entropy increases proportionally to the heat added.

Question 2

According to the second law of thermodynamics, which of the following statements is true?

Accepted Answer

The total entropy of an isolated system always increases or remains constant over time.

Answer

Heat flows spontaneously from cold to hot objects.

Answer

All processes can be completely efficient.

Answer

The total energy of the universe is decreasing.

Question 3

In thermodynamics, which of the following is NOT considered a thermodynamic system?

Accepted Answer

Black hole

Answer

Closed system

Answer

Open system

Answer

Isolated system

Question 4

Which of the following statements about the second law of thermodynamics is **false**?

Accepted Answer

Heat flows spontaneously from a cold reservoir to a hot reservoir.

Answer

Entropy increases in irreversible processes.

Answer

Heat engines cannot operate with perfect efficiency.

Answer

The second law of thermodynamics helps us predict the direction of spontaneous processes.

Question 5

Which of the following best describes an adiabatic process?

Accepted Answer

A process with no heat transfer

Answer

A process with constant temperature

Answer

A process that occurs in a closed system

Answer

A process that is the same as an isothermal process

Question 6

In thermodynamics, which process maintains constant entropy?

Accepted Answer

Isentropic process

Answer

Isothermal process

Answer

Adiabatic process

Answer

Isochoric process

Question 7

According to the First Law of Thermodynamics, which of the following is NOT a way energy can move across the boundary of a closed system?

Accepted Answer

Mass transfer

Answer

Work

Answer

Heat

Answer

Radiation

Question 8

In an isothermal process, the work done by the system is:

Accepted Answer

Equal to the heat transferred

Answer

Greater than the heat transferred

Answer

Less than the heat transferred

Answer

Unrelated to the heat transferred

Question 9

According to the first law of thermodynamics, what happens to the total energy of an isolated system?

Accepted Answer

It remains constant.

Answer

It can be created or destroyed.

Answer

Its efficiency can be determined.

Answer

It applies only to closed systems.

Question 10

An ideal gas undergoes a closed, isentropic process. Which of the following is true about this process?

Accepted Answer

No heat exchange occurs.

Answer

Entropy decreases.

Answer

Temperature increases.

Answer

Internal energy increases.

Question 11

According to the First Law of Thermodynamics, energy:

Accepted Answer

Can neither be created nor destroyed

Answer

Can be created or destroyed

Answer

Can be created but not destroyed

Answer

Can be destroyed but not created

Question 12

In a closed thermodynamic system, what happens to the internal energy?

Accepted Answer

Remains constant without external work or heat transfer.

Answer

Increases only by adding heat.

Answer

Decreases only by extracting work.

Answer

Is always positive and cannot be reduced.

Question 13

In an isobaric process, where pressure remains constant, how does the enthalpy change of the system relate to the heat added to the system?

Accepted Answer

Enthalpy change equals heat added.

Answer

Enthalpy change equals work done.

Answer

Enthalpy change equals internal energy change.

Answer

Enthalpy change is zero.

Question 14

Which property is NOT a defining characteristic of a thermodynamic system?

Accepted Answer

Presence of non-equilibrium conditions

Answer

Tendency towards thermal equilibrium

Answer

Conservation of mass and energy

Answer

Transfer of energy as heat and work

Question 15

According to the second law of thermodynamics, what occurs to the entropy of an isolated system experiencing an irreversible process?

Accepted Answer

Entropy increases.

Answer

Entropy decreases.

Answer

Entropy stays the same.

Question 16

Which system does NOT meet the criteria for a closed system in thermodynamics?

Accepted Answer

A room with an open window

Answer

A sealed container filled with gas

Answer

A piston-cylinder assembly with a fixed piston

Answer

An isolated container with no heat or mass transfer

Question 17

Which heat transfer mechanism involves the transfer of energy primarily through electromagnetic waves?

Accepted Answer

Radiation

Answer

Conduction

Answer

Convection

Answer

Nusselt number

Question 18

Calculate the efficiency of a heat engine, which is the ratio of the net work output to the heat input.

Accepted Answer

Efficiency = (Heat input - Heat output) / Heat input

Answer

Efficiency = Heat input / Heat output

Answer

Efficiency = Heat output / Heat input + 1

Answer

Efficiency = (Heat output + Heat input) / Heat input

Question 19

In the Otto cycle, which process involves adding heat at constant volume, resulting in an increase in both temperature and pressure of the working fluid?

Accepted Answer

Heat addition

Answer

Compression

Answer

Expansion

Answer

Heat rejection

Question 20

In a closed system undergoing an isothermal process, what occurs to the internal energy change of an ideal gas?

Accepted Answer

Remains constant

Answer

Increases

Answer

Decreases

Question 21

In a Rankine cycle, what is the primary function of the condenser?

Accepted Answer

Condense steam from the turbine back into liquid water

Answer

Convert high-pressure water into high-pressure steam

Answer

Heat the working fluid before entering the turbine

Answer

Expand the working fluid, converting pressure energy into kinetic energy

Question 22

In an isothermal process, the temperature of the system remains constant. What is the relationship between heat capacity and temperature in this process?

Accepted Answer

Heat capacity is independent of the change in temperature.

Answer

Heat capacity is directly proportional to the change in temperature.

Answer

Heat capacity is inversely proportional to the change in temperature.

Answer

Heat capacity is undefined in isothermal processes.

Question 23

What is the definition of efficiency for a heat engine?

Accepted Answer

Work output divided by heat input

Answer

Heat input divided by work output

Answer

Heat rejected divided by heat input

Question 24

What is a key distinction between **Enthalpy** and **Internal Energy**?

Accepted Answer

Enthalpy includes volume-related energy, unlike internal energy.

Answer

Internal energy includes volume-related energy, unlike enthalpy.

Answer

Enthalpy applies only to open systems, while internal energy applies to both open and closed systems.

Answer

Internal energy applies only to closed systems, while enthalpy applies to both open and closed systems.

Question 25

The first law of thermodynamics states that:

Accepted Answer

Energy can only be transferred or transformed.

Answer

Energy can be created or destroyed.

Answer

Heat flows from cold to hot.

Answer

The efficiency of a heat engine can be 100%.

Question 26

The SI unit of entropy is:

Accepted Answer

Joule per Kelvin

Answer

Watt per Kelvin

Answer

Newton per Kelvin

Answer

Pascal per Kelvin

Question 27

The relationship between enthalpy and internal energy is:

Accepted Answer

Enthalpy equals internal energy plus PV

Answer

Internal energy equals enthalpy minus PV

Answer

Enthalpy is proportional to internal energy

Answer

Internal energy is proportional to enthalpy

Question 28

The difference between a closed and an open system in thermodynamics is:

Accepted Answer

A closed system can exchange energy but not mass, while an open system can exchange both.

Answer

An open system can exchange energy but not mass, while a closed system can exchange both.

Answer

A closed system cannot exchange energy or mass, while an open system can exchange both.

Answer

An open system cannot exchange energy or mass, while a closed system can exchange both.

Question 29

The Gibbs free energy represents:

Accepted Answer

The maximum work that can be extracted from a system at constant temperature and pressure

Answer

The minimum work that must be done on a system to bring it to a desired state

Answer

The difference between the enthalpy and the entropy of a system

Answer

The sum of the internal energy and the entropy of a system

Question 30

A process that results in a decrease in entropy is:

Accepted Answer

Condensation of steam

Answer

Melting of ice

Answer

Vaporization of water

Answer

Sublimation of dry ice

Question 31

During an isothermal process of an ideal gas, which of the following remains constant?

Accepted Answer

Temperature

Answer

Pressure

Answer

Volume

Answer

Entropy

Question 32

Which of the following is NOT considered a thermodynamic system?

Accepted Answer

An isolated person sitting in a room

Answer

A closed gas in a sealed container

Answer

A mixture of liquids in a stirred beaker

Answer

A car engine running at steady speed

Question 33

Which of the following statements accurately describes the first law of thermodynamics?

Accepted Answer

The change in internal energy of a system equals the heat added to the system minus the work done by the system.

Answer

Energy can neither be created nor destroyed.

Answer

Heat always flows from hot to cold objects.

Answer

Entropy always decreases in spontaneous processes.

Question 34

Which thermodynamic process is characterized by constant entropy?

Accepted Answer

Adiabatic reversible compression

Answer

Adiabatic irreversible compression

Answer

Isothermal compression

Answer

Isochoric compression

Question 35

Which of the following processes occurs spontaneously?

Accepted Answer

A gas expanding into a vacuum

Answer

Water flowing uphill

Answer

Heat flowing from a cold object to a hot object

Answer

A battery recharging

Question 36

Which of the following best defines the Carnot cycle in thermodynamics?

Accepted Answer

An idealized cycle with maximum efficiency

Answer

A cycle that converts heat into work

Answer

A cycle that converts work into heat

Answer

A cycle used to measure temperature

Question 37

Which law of thermodynamics states that the entropy of an isolated system always increases over time?

Accepted Answer

Second law

Answer

First law

Answer

Third law

Answer

Zeroth law

Question 38

In a closed system undergoing an irreversible process, what happens to the entropy?

Accepted Answer

Increases

Answer

Decreases

Answer

Stays the same

Answer

Drops to zero

Question 39

According to the first law of thermodynamics, what happens to the total energy of an isolated system?

Accepted Answer

It remains constant.

Answer

It can be created or destroyed.

Answer

It always flows from a colder object to a hotter object.

Answer

It always decreases.

Question 40

Which of the following is not a property of a thermodynamic system?

Accepted Answer

Mass

Answer

Temperature

Answer

Pressure

Answer

Volume

Question 41

Which of the following processes is isobaric?

Accepted Answer

A gas expanding in a cylinder with a movable piston

Answer

A gas expanding in a sealed container

Answer

A gas flowing through a pipe with friction

Answer

A gas undergoing a chemical reaction

Question 42

Entropy is a measure of:

Accepted Answer

Disorder or randomness

Answer

Energy

Answer

Temperature

Answer

Volume

Question 43

Which of the following is a reversible process?

Accepted Answer

A gas expanding in a cylinder with a frictionless piston

Answer

A gas expanding in a sealed container

Answer

A gas flowing through a pipe with friction

Answer

A gas undergoing a chemical reaction

Question 44

The free energy of a system is the:

Accepted Answer

Maximum amount of work that can be done by the system

Answer

Minimum amount of work that must be done on the system

Answer

Change in internal energy of the system

Answer

Change in entropy of the system

Question 45

Which of the following is a closed system?

Accepted Answer

A gas expanding in a sealed container

Answer

A gas expanding in a cylinder with a movable piston

Answer

A gas flowing through a pipe

Answer

A gas undergoing a chemical reaction

Question 46

The efficiency of a heat engine is:

Accepted Answer

The ratio of the work done by the engine to the heat input

Answer

The ratio of the heat input to the work done by the engine

Answer

The difference between the heat input and the heat output

Answer

The sum of the heat input and the heat output

Question 47

How does the change in Gibbs free energy indicate the spontaneity of a chemical reaction?

Accepted Answer

A negative change indicates a spontaneous reaction.

Answer

A positive change indicates a spontaneous reaction.

Answer

The change is unrelated to spontaneity.

Answer

A zero change indicates a spontaneous reaction.

Question 48

Identify the statement that does NOT describe a thermodynamic system:

Accepted Answer

A system that undergoes a cyclic process

Answer

A closed system

Answer

An open system

Answer

A system that is isolated from its environment

Question 49

Which statement accurately defines the first law of thermodynamics?

Accepted Answer

Energy can neither be created nor destroyed, but it can be transferred or transformed.

Answer

The total energy of an isolated system remains constant.

Answer

Entropy always increases in an isolated system, leading to disorder.

Answer

Heat will always flow from a hotter object to a colder object.

Question 50

Which concept in thermodynamics measures the disorder or randomness within a system?

Accepted Answer

Entropy

Answer

Temperature

Answer

Volume

Answer

Pressure

Question 51

Define enthalpy in the context of thermodynamics:

Accepted Answer

The heat content of the system

Answer

The total energy of the system

Answer

The work done by the system

Answer

The entropy of the system

Question 52

Which thermodynamic process is characterized by constant entropy?

Accepted Answer

Isothermal compression

Answer

Adiabatic expansion

Answer

Isochoric heating

Answer

Isobaric cooling

Question 53

Identify the condition that must be met for a process to occur spontaneously:

Accepted Answer

Negative change in free energy

Answer

Positive change in entropy

Answer

Increase in temperature

Answer

Decrease in pressure

Question 54

What is the theoretical maximum efficiency of a heat engine, as defined by the Carnot efficiency?

Accepted Answer

The highest possible efficiency achievable

Answer

Ratio of heat absorbed to heat rejected

Answer

Ratio of work done to heat absorbed

Answer

Efficiency of an isothermal process

Question 55

Describe the fundamental principle behind a refrigeration cycle:

Accepted Answer

Heat transfer from a hot reservoir to a cold reservoir

Answer

Heat transfer from a cold reservoir to a hot reservoir

Answer

Conversion of mechanical energy into thermal energy

Answer

Conversion of thermal energy into mechanical energy

Question 56

The standard unit for work in the International System of Units (SI) is:

Accepted Answer

Joule

Answer

Newton

Answer

Watt

Answer

Kelvin

Question 57

In an ideal gas model, which of the following is NOT assumed?

Accepted Answer

Particles have no interactions with each other.

Answer

Particles have negligible volume.

Answer

Particles move randomly and independently.

Answer

Collisions between particles are perfectly elastic.

Question 58

Entropy is a measure of:

Accepted Answer

Disorder or randomness within a system

Answer

Heat energy per unit temperature

Answer

Internal energy per unit mass

Answer

Work done per unit volume

Question 59

An isentropic process is one where:

Accepted Answer

Entropy remains constant.

Answer

Temperature remains constant.

Answer

Pressure remains constant.

Answer

Volume remains constant.

Question 60

The Gibbs free energy represents:

Accepted Answer

The maximum amount of work that can be obtained from a system at constant temperature and pressure.

Answer

The change in enthalpy at constant pressure.

Answer

The change in entropy at constant temperature.

Answer

The change in internal energy at constant volume.

Question 61

A closed system is characterized by:

Accepted Answer

No mass or energy transfer with the surroundings.

Answer

Only mass transfer with the surroundings.

Answer

Only energy transfer with the surroundings.

Answer

Both mass and energy transfer with the surroundings.

Question 62

The fundamental difference between heat and work lies in:

Accepted Answer

Heat is a form of energy transfer due to a temperature difference, while work is a form of energy transfer due to a force acting through a distance.

Answer

Heat is a form of energy transfer due to a force acting through a distance, while work is a form of energy transfer due to a temperature difference.

Answer

Heat and work are interchangeable forms of energy.

Answer

Heat and work are unrelated forms of energy.

Question 63

A Carnot cycle is a theoretical heat engine cycle that operates:

Accepted Answer

Between two constant-temperature reservoirs and involves two isothermal and two adiabatic processes.

Answer

Between two constant-pressure reservoirs and involves two isobaric and two adiabatic processes.

Answer

Between two constant-volume reservoirs and involves two isochoric and two adiabatic processes.

Answer

Between two constant-entropy reservoirs and involves two isentropic and two adiabatic processes.

Question 64

The efficiency of a heat engine operating between two thermal reservoirs is:

Accepted Answer

The ratio of the work output to the heat input.

Answer

The ratio of the heat input to the work output.

Answer

The difference in temperature between the two reservoirs.

Answer

The sum of the temperatures of the two reservoirs.