Applications of Thermodynamics: Power Cycles, Refrigeration, and Combustion Engines

Question 1

What is the theoretical efficiency of a Carnot heat engine operating between temperatures T1 and T2?

Accepted Answer

1 - (T2/T1)

Answer

(T1 - T2)/T2

Answer

(T1 - T2)/T1

Answer

(T2 - T1)/T1

Question 2

What is the primary function of an expansion valve in a refrigeration cycle?

Accepted Answer

To regulate the flow of refrigerant

Answer

To condense the refrigerant

Answer

To evaporate the refrigerant

Answer

To separate the refrigerant from the lubricant

Question 3

Which of the following distinguishes a heat pump from an air conditioner?

Accepted Answer

A heat pump transfers heat from a hot reservoir to a cold reservoir, while an air conditioner does the opposite.

Answer

A heat pump uses a compressor, while an air conditioner uses a fan.

Answer

A heat pump is more efficient than an air conditioner.

Answer

A heat pump can only be used for heating, while an air conditioner can be used for both heating and cooling.

Question 4

Which type of combustion engine utilizes spark plugs to ignite the fuel-air mixture?

Accepted Answer

Gasoline engine

Answer

Diesel engine

Answer

Rotary engine

Answer

Stirling engine

Question 5

Which of the following is NOT a factor influencing the efficiency of a combustion engine?

Accepted Answer

Ambient temperature

Answer

Fuel-air ratio

Answer

Compression ratio

Answer

Valve timing

Question 6

What is the purpose of a catalytic converter in a combustion engine exhaust system?

Accepted Answer

To reduce emissions of harmful pollutants

Answer

To improve fuel economy

Answer

To increase engine power

Answer

To reduce engine noise

Question 7

In a refrigeration system, the condenser's primary function is to:

Accepted Answer

Release heat to the surroundings

Answer

Absorb heat from the refrigerant

Answer

Compress the refrigerant

Answer

Expand the refrigerant

Question 8

The first law of thermodynamics fundamentally states the principle of:

Accepted Answer

Conservation of energy

Answer

Entropy increase

Answer

Heat transfer

Answer

Work done by a system

Question 9

Which thermodynamic process occurs at constant temperature?

Accepted Answer

Constant-pressure heat addition

Answer

Adiabatic compression

Answer

Isochoric expansion

Answer

Constant-volume heat rejection

Question 10

In a substance's phase diagram, the critical point signifies the conditions where:

Accepted Answer

Liquid and gas phases become indistinguishable

Answer

The substance reaches its highest possible temperature

Answer

The substance experiences its highest pressure

Answer

The substance has its lowest possible volume

Question 11

In a Rankine cycle, which process transforms liquid water into saturated vapor?

Accepted Answer

Isobaric heat addition

Answer

Adiabatic compression

Answer

Isothermal expansion

Answer

Adiabatic expansion

Question 12

What metric quantifies the efficiency of a heat pump?

Accepted Answer

Coefficient of performance (COP)

Answer

Thermal efficiency

Answer

Power density

Answer

Specific heat capacity

Question 13

Which engine type converts chemical energy from fuel into mechanical energy through controlled combustion?

Accepted Answer

Internal combustion engine

Answer

External combustion engine

Answer

Steam turbine

Answer

Fuel cell

Question 14

In which application is the Otto cycle commonly employed?

Accepted Answer

Spark-ignition gasoline engines

Answer

Diesel engines

Answer

Turbine engines

Answer

Refrigeration systems

Question 15

In a combustion engine, which process raises the pressure and temperature of the air-fuel mixture?

Accepted Answer

Compression stroke

Answer

Power stroke

Answer

Exhaust stroke

Answer

Intake stroke

Question 16

What is the primary function of a refrigeration cycle?

Accepted Answer

To extract heat from a cold reservoir and transfer it to a hot reservoir.

Answer

To heat a cold reservoir.

Answer

To cool a hot reservoir.

Question 17

What fundamental difference distinguishes a closed-loop refrigeration cycle from an open-loop refrigeration cycle?

Accepted Answer

In a closed-loop cycle, the refrigerant continuously circulates, while in an open-loop cycle, the refrigerant is not reused.

Answer

Closed-loop cycles are more prevalent than open-loop cycles.

Answer

Closed-loop cycles are inherently more efficient than open-loop cycles.

Question 18

What mathematical equation defines thermal efficiency for a heat engine?

Accepted Answer

Thermal Efficiency = (Work Output) / (Heat Input)

Answer

Thermal Efficiency = (Work Output) / (Heat Rejected)

Answer

Thermal Efficiency = (Heat Input) / (Work Output)

Answer

Thermal Efficiency = (Heat Rejected) / (Work Output)

Question 19

Which assumption is fundamental to the ideal gas law?

Accepted Answer

Gas molecules possess negligible volume, and intermolecular forces are absent.

Answer

Gas molecules are perfectly elastic and collide elastically with each other.

Answer

Gas molecules move in straight lines and collide inelastically with each other.

Question 20

What is the significance of the critical point on a phase diagram?

Accepted Answer

The critical point marks the conditions at which the liquid and gas phases become indistinguishable.

Answer

The critical point represents the conditions at which the solid and liquid phases become indistinguishable.

Answer

The critical point indicates the conditions where the solid and gas phases become indistinguishable.

Question 21

Which of the following is a thermodynamic property?

Accepted Answer

Entropy

Answer

Acceleration

Answer

Force

Answer

Velocity

Question 22

Define Gibbs free energy.

Accepted Answer

Gibbs free energy is a thermodynamic potential combining enthalpy and entropy to determine the spontaneity of a reaction.

Answer

Gibbs free energy is a measure of the internal energy of a system.