Applications of First Law: Interactive Learning Quizzes for Thermodynamics

Question 1

Given that the specific heat capacity of water is 4.18 kJ/kg-K, how much heat is needed to raise the temperature of 1 kg of water from 20°C to 100°C?

Accepted Answer

334.4 kJ

Answer

418 kJ

Answer

672 kJ

Answer

836 kJ

Question 2

Which of the following is a defining characteristic of an isentropic process?

Accepted Answer

Constant entropy

Answer

Constant temperature

Answer

Constant pressure

Answer

Constant volume

Question 3

Which of the following is a fundamental assumption of the First Law of Thermodynamics?

Accepted Answer

Energy is conserved

Answer

Entropy is constant

Answer

Temperature is uniform

Answer

Pressure is constant

Question 4

A heat exchanger is used to:

Accepted Answer

Transfer heat from one fluid to another

Answer

Generate electricity

Answer

Reduce pressure

Answer

Cool a system

Question 5

The efficiency of a heat engine is defined as:

Accepted Answer

The ratio of work output to heat input

Answer

The ratio of heat input to work output

Answer

The ratio of heat rejected to heat input

Answer

The ratio of heat rejected to work output

Question 6

Which of the following is an example of a reversible process?

Accepted Answer

Isothermal expansion of an ideal gas

Answer

Adiabatic compression of a gas

Answer

Heat transfer through a finite temperature difference

Answer

Friction

Question 7

The enthalpy of a system is:

Accepted Answer

The sum of its internal energy and pressure-volume product

Answer

The difference between its internal energy and pressure-volume product

Answer

The product of its temperature and heat capacity

Answer

The quotient of its heat capacity and temperature

Question 8

Which of the following is a characteristic of a spontaneous process?

Accepted Answer

It occurs without any external input of energy

Answer

It requires an external input of energy

Answer

It always results in an increase in entropy

Answer

It is always reversible

Question 9

The first law of thermodynamics is a statement of:

Accepted Answer

Conservation of energy

Answer

Conservation of mass

Answer

Conservation of momentum

Answer

Entropy

Question 10

Which of the following is an example of an isentropic process?

Accepted Answer

Adiabatic expansion of an ideal gas

Answer

Isothermal compression of a gas

Answer

Heat transfer through a finite temperature difference

Answer

Friction

Question 11

An insulated container contains an ideal gas. Heat is added to the gas, causing its temperature to rise. What is the change in internal energy of the gas?

Accepted Answer

Positive

Answer

Negative

Answer

Zero

Answer

Cannot be determined without knowing the specific heat capacity of the gas

Question 12

A heat engine operates between a high-temperature reservoir at 800 K and a low-temperature reservoir at 300 K. Assuming the engine is reversible, what is its maximum possible efficiency?

Accepted Answer

37.5%

Answer

25%

Answer

50%

Answer

62.5%

Question 13

Which of the following factors has the greatest impact on the efficiency of a steam turbine?

Accepted Answer

Temperature of the steam entering the turbine

Answer

Pressure of the steam entering the turbine

Answer

Speed of rotation of the turbine

Answer

Number of stages in the turbine

Question 14

Which of the following statements about the First Law of Thermodynamics is incorrect?

Accepted Answer

Entropy always decreases in an isolated system.

Answer

Energy can neither be created nor destroyed.

Answer

Heat and work are equivalent forms of energy.

Answer

Energy can be transferred from one system to another.

Question 15

A throttling process, also known as an isenthalpic process, is one in which:

Accepted Answer

Enthalpy remains constant.

Answer

Internal energy remains constant.

Answer

Entropy remains constant.

Answer

Temperature remains constant.

Question 16

Which of the following is NOT an area where the First Law of Thermodynamics finds application in engineering?

Accepted Answer

Simulation of fluid dynamics

Answer

Design of efficient power plants

Answer

Analysis of refrigeration systems

Answer

Development of combustion engines

Question 17

The entropy change of a closed system undergoing an irreversible process is:

Accepted Answer

Always positive.

Answer

Always negative.

Answer

Zero.

Answer

Uncertain.

Question 18

Which of the following heat engines operates with the highest theoretical efficiency?

Accepted Answer

Carnot engine

Answer

Stirling engine

Answer

Otto engine

Answer

Diesel engine

Question 19

A heat pump operates between two reservoirs with temperatures of 300 K and 400 K, respectively. What is its maximum possible coefficient of performance?

Accepted Answer

1.33

Answer

1

Answer

2

Answer

3

Question 20

For a closed system undergoing a reversible cycle consisting of adiabatic and isobaric processes, what is the overall entropy change over the cycle?

Accepted Answer

0

Answer

Positive

Answer

Negative

Answer

Cannot be determined

Question 21

Which of the following is NOT a fundamental principle of the First Law of Thermodynamics?

Accepted Answer

Heat and work are the only forms of energy.

Answer

Energy can neither be created nor destroyed.

Answer

Energy can be transferred and transformed.

Answer

The total energy of an isolated system remains constant.

Question 22

An engine receives 200 kJ of heat and does 120 kJ of work. What is the thermal efficiency of the engine?

Accepted Answer

50%

Answer

40%

Answer

60%

Answer

70%

Question 23

Which of the following devices converts heat energy into electrical energy?

Accepted Answer

Thermoelectric generator

Answer

Heat pump

Answer

Refrigerator

Answer

Air conditioner

Question 24

Which of the following is an example of a reversible process?

Accepted Answer

Melting ice at constant pressure

Answer

Stirring a cup of coffee

Answer

Mixing two different gases

Answer

Charging a battery

Question 25

For a closed system undergoing a process, the change in its internal energy is equal to:

Accepted Answer

Heat added - Work done

Answer

Work done - Heat added

Answer

Heat added + Work done

Answer

Work done + Heat added

Question 26

A closed system undergoes a process where the heat transferred into the system is 500 kJ. The work done by the system during the process is 200 kJ. What is the change in internal energy of the system?

Accepted Answer

300 kJ

Answer

500 kJ

Answer

-300 kJ

Answer

-500 kJ

Question 27

A heat engine operates between a high-temperature reservoir at 600 K and a low-temperature reservoir at 300 K. What is the maximum possible efficiency of this heat engine?

Accepted Answer

66.7%

Answer

20%

Answer

50%

Answer

100%

Question 28

In an adiabatic closed system, heat transfer is:

Accepted Answer

Zero

Answer

Negative out of the system

Answer

Indeterminate

Answer

Positive into the system

Question 29

The thermal efficiency of a heat engine is defined as:

Accepted Answer

The ratio of work output to heat input

Answer

The ratio of work input to heat input

Answer

The ratio of heat input to work output

Answer

The ratio of heat output to heat input

Question 30

An isothermal process is one in which:

Accepted Answer

Temperature remains constant

Answer

Pressure remains constant

Answer

Volume remains constant

Answer

Internal energy remains constant

Question 31

In a cycle, the net work done by a gas is equal to:

Accepted Answer

The area enclosed by the cycle on a P-V diagram

Answer

The change in volume of the gas

Answer

The heat added to the gas

Answer

The change in internal energy of the gas

Question 32

In a throttling process, the:

Accepted Answer

Enthalpy remains constant

Answer

Volume remains constant

Answer

Temperature remains constant

Answer

Pressure remains constant

Question 33

Which of the following is an example of a closed system?

Accepted Answer

A sealed container filled with gas

Answer

A car engine

Answer

A room with an open window

Answer

A boiling pot of water

Question 34

Which of the following describes a reversible process?

Accepted Answer

A process that can be reversed without any change to the system or surroundings

Answer

A process that releases heat to the surroundings

Answer

A process that increases the entropy of the system

Answer

A process that decreases the internal energy of the system

Question 35

A closed system undergoes a reversible adiabatic process. Which of the following statements is correct about its entropy?

Accepted Answer

It remains constant.

Answer

It increases.

Answer

It decreases.

Answer

It becomes zero.

Question 36

An open system undergoes a steady-state process. The mass flow rate into the system is 1 kg/s. The specific enthalpy of the fluid entering the system is 500 kJ/kg. The heat transfer to the system is 200 kW. What is the specific enthalpy of the fluid exiting the system?

Accepted Answer

700 kJ/kg

Answer

100 kJ/kg

Answer

900 kJ/kg

Answer

300 kJ/kg

Question 37

A piston-cylinder device contains 1 kg of air initially at 100 kPa and 27°C. The air undergoes an adiabatic compression process until its final pressure reaches 700 kPa. Determine the work done on the air during the compression. Assume air to be an ideal gas with constant specific heats (C_v = 0.718 kJ/kg·K, C_p = 1.005 kJ/kg·K).

Accepted Answer

The work done on the air is -174.6 kJ.

Answer

The work done on the air is -287.3 kJ.

Answer

The work done on the air is 287.3 kJ.

Answer

The work done on the air is 174.6 kJ.

Question 38

A well-insulated rigid tank contains 2 kg of air at 200 kPa and 20°C. A paddle wheel inside the tank stirs the air until its temperature rises to 50°C. Determine the work done by the paddle wheel on the air. Assume air to be an ideal gas with constant specific heats (C_v = 0.718 kJ/kg·K, C_p = 1.005 kJ/kg·K).

Accepted Answer

The work done by the paddle wheel is 430.8 kJ.

Answer

The work done by the paddle wheel is -588.6 kJ.

Answer

The work done by the paddle wheel is -430.8 kJ.

Answer

The work done by the paddle wheel is 588.6 kJ.

Question 39

A closed system undergoes a thermodynamic cycle consisting of three processes: (1) isothermal expansion, (2) isobaric cooling, and (3) isochoric heating. Which of the following statements is true about the net work done during the cycle?

Accepted Answer

The net work done during the cycle is positive.

Answer

The net work done during the cycle is zero.

Answer

The net work done during the cycle cannot be determined without more information.

Answer

The net work done during the cycle is negative.

Question 40

A heat engine operates between two reservoirs at temperatures of 800 K and 300 K. Calculate the maximum possible thermal efficiency of this engine.

Accepted Answer

The maximum possible thermal efficiency of the engine is 62.5%.

Answer

The maximum possible thermal efficiency of the engine is 0%.

Answer

The maximum possible thermal efficiency of the engine is 37.5%.

Answer

The maximum possible thermal efficiency of the engine is 100%.

Question 41

A 10 kW electric heater is used to heat a room. The temperature of the room increases by 5°C after 1 hour of operation. Assuming no heat loss to the surroundings, determine the heat capacity of the room.

Accepted Answer

The heat capacity of the room is 36 MJ/°C.

Answer

The heat capacity of the room is 18 MJ/°C.

Answer

The heat capacity of the room is 36 kJ/°C.

Answer

The heat capacity of the room is 18 kJ/°C.

Question 42

A 100% efficient and fully reversible heat engine operates between two reservoirs at temperatures of 1000 K and 300 K. Calculate the amount of heat rejected to the cold reservoir when 100 kJ of heat is absorbed from the hot reservoir.

Accepted Answer

The amount of heat rejected to the cold reservoir is 30 kJ.

Answer

The amount of heat rejected to the cold reservoir is 70 kJ.

Answer

The amount of heat rejected to the cold reservoir is 100 kJ.

Question 43

A system undergoes a process where the internal energy increases by 200 kJ. If 100 kJ of heat is transferred to the system during the process, determine the work done by the system.

Accepted Answer

The work done by the system is -100 kJ.

Answer

The work done by the system is -300 kJ.

Answer

The work done by the system is 300 kJ.

Answer

The work done by the system is 100 kJ.