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1. Thermodynamics is primarily the study of which of the following?
ⓐ. Motion of planets
ⓑ. Transformation of heat and work
ⓒ. Structure of atoms
ⓓ. Laws of electricity
Correct Answer: Transformation of heat and work
Explanation: Thermodynamics is the branch of physics that deals with the relationship between heat, work, and internal energy. It explains how energy is transferred in different forms and is governed by specific laws. The other options belong to different branches of physics like astronomy, atomic physics, and electromagnetism.
2. Which of the following is an example of a thermodynamic system?
ⓐ. A football moving in air
ⓑ. Gas in a closed cylinder with a piston
ⓒ. A stone falling from a height
ⓓ. A magnet attracting iron filings
Correct Answer: Gas in a closed cylinder with a piston
Explanation: A thermodynamic system is a defined region where energy interactions are studied. Gas in a closed cylinder is a system where heat and work transfer can be measured. A football or stone describes mechanics, and magnetism relates to electromagnetism, not thermodynamics.
3. In thermodynamics, what does the term “surroundings” mean?
ⓐ. The walls of the container
ⓑ. Everything outside the system boundary
ⓒ. Only the air around the system
ⓓ. Only the environment at room temperature
Correct Answer: Everything outside the system boundary
Explanation: Surroundings refer to everything external to the chosen system, which can interact with it through heat or work. It is not limited to the container walls or just air, but all external factors beyond the system boundary.
4. Which of the following quantities is a state function?
ⓐ. Work
ⓑ. Heat
ⓒ. Internal Energy
ⓓ. Path length
Correct Answer: Internal Energy
Explanation: A state function depends only on the state of the system, not on how it was achieved. Internal energy depends on parameters like pressure, volume, and temperature. Work and heat are path functions, as they depend on the process taken, not just the final state.
5. Which law of thermodynamics introduces the concept of temperature?
ⓐ. Zeroth Law
ⓑ. First Law
ⓒ. Second Law
ⓓ. Third Law
Correct Answer: Zeroth Law
Explanation: The Zeroth Law of Thermodynamics states that if two systems are in thermal equilibrium with a third, they are in equilibrium with each other. This law forms the basis of defining temperature. The First Law deals with energy conservation, the Second with entropy, and the Third with absolute zero.
6. What is the First Law of Thermodynamics also known as?
ⓐ. Law of entropy
ⓑ. Law of energy conservation
ⓒ. Law of cooling
ⓓ. Law of absolute zero
Correct Answer: Law of energy conservation
Explanation: The First Law states that energy can neither be created nor destroyed, only transformed from one form to another. Mathematically, $\Delta U = Q – W$, where $\Delta U$ is change in internal energy, $Q$ is heat added, and $W$ is work done.
7. Which of the following is an isolated system?
ⓐ. A cup of hot tea on a table
ⓑ. Water in a closed thermos flask
ⓒ. Gas in a piston-cylinder with movable piston
ⓓ. A refrigerator cooling food
Correct Answer: Water in a closed thermos flask
Explanation: An isolated system does not exchange matter or energy with its surroundings. A thermos approximates isolation by minimizing heat and matter transfer. A cup of tea exchanges heat, gas in a piston exchanges work, and a refrigerator requires external work input.
8. Which quantity remains constant in an isothermal process?
ⓐ. Pressure
ⓑ. Volume
ⓒ. Temperature
ⓓ. Internal energy
Correct Answer: Temperature
Explanation: In an isothermal process, the temperature remains constant. Internal energy of an ideal gas depends only on temperature, so $\Delta U = 0$. Any heat added is completely converted into work. Pressure or volume may change depending on the conditions.
9. Which type of system exchanges both energy and matter with surroundings?
ⓐ. Closed system
ⓑ. Isolated system
ⓒ. Open system
ⓓ. Adiabatic system
Correct Answer: Open system
Explanation: An open system allows exchange of both matter and energy, like boiling water in an open pot. A closed system exchanges only energy (not matter), an isolated system exchanges neither, and an adiabatic system restricts heat transfer but can allow work exchange.
10. Which of the following is an intensive property in thermodynamics?
ⓐ. Volume
ⓑ. Internal energy
ⓒ. Temperature
ⓓ. Enthalpy
Correct Answer: Temperature
Explanation: Intensive properties do not depend on the size or mass of the system. Temperature, pressure, and density are intensive. Volume, enthalpy, and internal energy are extensive properties as they depend on the system’s size.
11. Who is considered the “Father of Thermodynamics” for laying the foundation of the subject?
ⓐ. Isaac Newton
ⓑ. Sadi Carnot
ⓒ. Rudolf Clausius
ⓓ. James Joule
Correct Answer: Sadi Carnot
Explanation: Sadi Carnot (1824) is regarded as the Father of Thermodynamics because he analyzed the efficiency of heat engines and introduced the Carnot cycle. Clausius later developed entropy, Joule demonstrated mechanical equivalent of heat, and Newton worked in mechanics, not thermodynamics.
12. What was James Prescott Joule’s key contribution to thermodynamics?
ⓐ. Law of Gravitation
ⓑ. Concept of Entropy
ⓒ. Mechanical Equivalent of Heat
ⓓ. Ideal Gas Law
Correct Answer: Mechanical Equivalent of Heat
Explanation: Joule showed that heat and mechanical work are interchangeable forms of energy, establishing the “mechanical equivalent of heat.” His paddle-wheel experiment linked work done to temperature rise. Entropy was introduced by Clausius, and the Ideal Gas Law was developed from Boyle’s and Gay-Lussac’s work.
13. Which scientist introduced the concept of entropy?
ⓐ. Rudolf Clausius
ⓑ. Lord Kelvin
ⓒ. Sadi Carnot
ⓓ. Boyle
Correct Answer: Rudolf Clausius
Explanation: In 1865, Rudolf Clausius introduced entropy as a measure of energy dispersal or disorder, and reformulated the Second Law of Thermodynamics. Carnot focused on heat engines, Kelvin defined absolute zero, and Boyle worked on gas laws.
14. Lord Kelvin’s greatest contribution to thermodynamics was:
ⓐ. Introducing entropy
ⓑ. Establishing the absolute temperature scale
ⓒ. Explaining Boyle’s Law
ⓓ. Inventing the steam engine
Correct Answer: Establishing the absolute temperature scale
Explanation: Lord Kelvin (William Thomson) proposed the absolute temperature scale, with zero at absolute zero, where molecular motion ceases. Entropy was introduced by Clausius, Boyle’s Law was given by Boyle, and steam engine improvements came from Watt, not Kelvin.
15. The Carnot theorem states that:
ⓐ. Energy can neither be created nor destroyed
ⓑ. Heat cannot flow from cold to hot without work
ⓒ. No engine can be more efficient than a Carnot engine operating between the same two temperatures
ⓓ. Internal energy depends only on state variables
Correct Answer: No engine can be more efficient than a Carnot engine operating between the same two temperatures
Explanation: Carnot’s theorem establishes the maximum theoretical efficiency of a heat engine between two temperature reservoirs. The First Law is option A, Clausius statement of Second Law is option B, and internal energy as state function is option D.
16. Who gave the First Law of Thermodynamics its modern form?
ⓐ. Rudolf Clausius
ⓑ. James Joule
ⓒ. Robert Mayer
ⓓ. Both B and C
Correct Answer: Both B and C
Explanation: Robert Mayer (1842) and James Joule independently developed the principle of conservation of energy, leading to the First Law of Thermodynamics. Clausius later gave its mathematical formulation.
17. Which 17th-century scientist first hinted at energy conservation through chemical processes?
ⓐ. Antoine Lavoisier
ⓑ. Robert Mayer
ⓒ. Galileo Galilei
ⓓ. Blaise Pascal
Correct Answer: Robert Mayer
Explanation: Robert Mayer observed that the bright red blood of sailors in the tropics indicated less oxygen use in hot climates, linking energy and heat conservation. This observation contributed to energy conservation theory, later formalized in the First Law.
18. In 1850, Clausius restated the Second Law of Thermodynamics as:
ⓐ. “Energy can neither be created nor destroyed.”
ⓑ. “Heat cannot of itself pass from a colder to a hotter body.”
ⓒ. “Entropy remains constant in a reversible process.”
ⓓ. “Work is the transfer of energy.”
Correct Answer: “Heat cannot of itself pass from a colder to a hotter body.”
Explanation: Clausius’s famous statement (1850) expresses the natural direction of heat transfer, forming one version of the Second Law. The First Law is option A, entropy constancy is another consequence, and option D defines work, not the law.
19. Which experiment directly established the mechanical equivalent of heat?
ⓐ. Fizeau’s light experiment
ⓑ. Joule’s paddle-wheel experiment
ⓒ. Carnot’s heat engine cycle
ⓓ. Lavoisier’s calorimeter experiment
Correct Answer: Joule’s paddle-wheel experiment
Explanation: Joule used a falling weight to drive paddles stirring water, showing that mechanical work raised water temperature. This quantified the mechanical equivalent of heat. Carnot developed theoretical cycles, while Lavoisier studied calorimetry without mechanical work.
20. The historical development of thermodynamics was mainly driven by:
ⓐ. Astronomy and optics
ⓑ. Development of heat engines during the Industrial Revolution
ⓒ. Discovery of electricity
ⓓ. Study of nuclear physics
Correct Answer: Development of heat engines during the Industrial Revolution
Explanation: Practical improvements in steam engines motivated scientists like Carnot, Joule, and Clausius to study heat-work relationships. Thermodynamics grew out of the need to improve efficiency in engines. Astronomy, electricity, and nuclear physics contributed to other fields but not directly to thermodynamics’ origin.
21. Why is thermodynamics important in engineering?
ⓐ. It explains the structure of the atom
ⓑ. It helps in designing efficient machines and engines
ⓒ. It only deals with astronomy
ⓓ. It is useful only in mathematics
Correct Answer: It helps in designing efficient machines and engines
Explanation: Thermodynamics provides the principles behind energy conversion, efficiency, and performance of machines such as heat engines, turbines, and refrigerators. It is not limited to astronomy or atomic structure, but is a core subject for engineers to optimize designs.
22. Which of the following fields heavily applies thermodynamic principles?
ⓐ. Civil engineering
ⓑ. Mechanical engineering
ⓒ. Electrical engineering
ⓓ. All of the above
Correct Answer: All of the above
Explanation: Thermodynamics is widely applied in civil (HVAC systems, building heat transfer), mechanical (engines, turbines), and electrical engineering (power plants, battery systems). Thus, it has interdisciplinary applications across all engineering fields.
23. In power plants, thermodynamics is mainly used to:
ⓐ. Study atomic structure
ⓑ. Maximize efficiency of converting heat into work
ⓒ. Minimize use of electricity
ⓓ. Increase gravitational force
Correct Answer: Maximize efficiency of converting heat into work
Explanation: Power plants operate based on thermodynamic cycles such as the Rankine cycle and Brayton cycle. Thermodynamics helps in reducing energy losses and maximizing work output from heat input. Other options are unrelated to power plant operations.
24. Which thermodynamic device is most directly linked to refrigeration and air conditioning systems?
ⓐ. Heat pump
ⓑ. Steam turbine
ⓒ. Diesel engine
ⓓ. Electric motor
Correct Answer: Heat pump
Explanation: Refrigerators and air conditioners operate on the principle of heat pumps, which transfer heat from low temperature to high temperature regions using external work. Turbines and diesel engines generate work, while motors convert electricity to motion.
25. Why is the study of entropy important in physical sciences?
ⓐ. It determines the size of molecules
ⓑ. It describes the disorder and irreversibility of natural processes
ⓒ. It helps calculate mass of atoms
ⓓ. It measures acceleration of objects
Correct Answer: It describes the disorder and irreversibility of natural processes
Explanation: Entropy is a key concept in the Second Law of Thermodynamics, showing the natural tendency of systems towards disorder. It also explains why certain processes, such as spontaneous heat flow, are irreversible.
26. Thermodynamics helps in chemical engineering mainly by:
ⓐ. Explaining the nuclear structure
ⓑ. Predicting direction and extent of chemical reactions
ⓒ. Calculating gravitational force between atoms
ⓓ. Designing optical instruments
Correct Answer: Predicting direction and extent of chemical reactions
Explanation: In chemical engineering, thermodynamics is used to calculate Gibbs free energy, enthalpy, and entropy changes, which determine whether reactions are spontaneous and to what extent they proceed. Other options are unrelated to chemical engineering.
27. In aerospace engineering, thermodynamics is essential for:
ⓐ. Designing wings for lift
ⓑ. Calculating thrust and fuel efficiency of jet engines
ⓒ. Measuring gravitational pull of planets
ⓓ. Developing navigation systems
Correct Answer: Calculating thrust and fuel efficiency of jet engines
Explanation: Jet engines operate on thermodynamic principles (Brayton cycle). Thermodynamics is crucial for evaluating efficiency, thrust production, and fuel consumption, making it central to aerospace engineering.
28. In which medical application does thermodynamics play a role?
ⓐ. X-ray imaging
ⓑ. MRI scanning
ⓒ. Cryogenics for preserving biological samples
ⓓ. Genetic sequencing
Correct Answer: Cryogenics for preserving biological samples
Explanation: Thermodynamics is important in cryogenics, where very low temperatures are used to preserve biological materials. MRI involves magnetic resonance, and genetic sequencing involves molecular biology, not thermodynamics.
29. The efficiency of car engines is limited due to:
ⓐ. Newton’s laws of motion
ⓑ. Maxwell’s equations
ⓒ. Second Law of Thermodynamics
ⓓ. Law of gravitation
Correct Answer: Second Law of Thermodynamics
Explanation: The Second Law states that no engine can be 100% efficient, as some energy is always lost as waste heat. This limits the efficiency of real-life car engines, regardless of design improvements.
30. In physical sciences, thermodynamics is significant because it:
ⓐ. Describes only mechanical motion
ⓑ. Provides universal laws governing energy transformations
ⓒ. Explains only atomic theory
ⓓ. Is restricted to heat transfer in solids
Correct Answer: Provides universal laws governing energy transformations
Explanation: Thermodynamics applies to gases, liquids, solids, and radiation, providing a universal framework for energy transformation in physical sciences. It is not restricted to mechanical motion or atomic theory alone.
31. Which of the following is NOT considered a thermodynamic system?
ⓐ. Gas enclosed in a piston-cylinder arrangement
ⓑ. Water boiling in an open vessel
ⓒ. A block sliding down an inclined plane
ⓓ. A sealed thermos flask with tea
Correct Answer: A block sliding down an inclined plane
Explanation: A thermodynamic system is defined as a portion of matter or space chosen for analysis where exchanges of energy and/or matter are considered. Gas in a cylinder, boiling water, and tea in a thermos all involve energy transfer in the form of heat or work, making them thermodynamic systems. A block sliding down an inclined plane involves only mechanics (kinetic and potential energy changes) but no heat-work transformation, so it is not considered a thermodynamic system.
32. In thermodynamics, which of the following is a path function?
ⓐ. Internal Energy
ⓑ. Enthalpy
ⓒ. Work
ⓓ. Pressure
Correct Answer: Work
Explanation: Path functions depend on the process followed to reach a state, not only on the state itself. Work and heat are classic path functions because their values vary with the path taken between two states (e.g., expansion at constant pressure vs. varying pressure). In contrast, internal energy, enthalpy, pressure, and temperature are state functions; they depend only on the state of the system and not on the history of the process.
33. The Zeroth Law of Thermodynamics allows us to define:
ⓐ. Heat capacity
ⓑ. Temperature scale
ⓒ. Work done in a process
ⓓ. Entropy
Correct Answer: Temperature scale
Explanation: The Zeroth Law states that if two systems are each in thermal equilibrium with a third, they are in equilibrium with each other. This establishes temperature as a measurable property and allows the construction of scales like Celsius, Kelvin, and Fahrenheit. Without this law, the concept of temperature would lack a scientific basis. Work, entropy, and heat capacity come under later laws, not the Zeroth Law.
34. The First Law of Thermodynamics is mathematically expressed as:
ⓐ. $\Delta U = Q + W$
ⓑ. $\Delta U = Q – W$
ⓒ. $\Delta U = W – Q$
ⓓ. $\Delta U = PV$
Correct Answer: $\Delta U = Q – W$
Explanation: The First Law states that the change in internal energy ($\Delta U$) of a system equals the heat supplied to the system ($Q$) minus the work done by the system ($W$) on its surroundings. The negative sign before work ensures the conservation of energy principle: if the system does work, its energy decreases unless compensated by heat input. Option A would apply if sign convention is reversed (work done on the system). Option D is an equation of state, not the First Law.
35. The Second Law of Thermodynamics introduces the concept of:
ⓐ. Energy conservation
ⓑ. Temperature
ⓒ. Entropy
ⓓ. Pressure
Correct Answer: Entropy
Explanation: The Second Law explains why some processes are irreversible and introduces entropy, a measure of disorder or unavailable energy. For example, heat naturally flows from hot to cold but never spontaneously the other way. This law provides the arrow of time in physics, distinguishing real processes from ideal reversible ones. Energy conservation belongs to the First Law, while temperature is introduced in the Zeroth Law.
36. The Third Law of Thermodynamics states that:
ⓐ. Entropy of a system approaches zero as temperature approaches absolute zero
ⓑ. Energy can neither be created nor destroyed
ⓒ. Heat cannot spontaneously flow from cold to hot
ⓓ. No engine can be more efficient than a Carnot engine
Correct Answer: Entropy of a system approaches zero as temperature approaches absolute zero
Explanation: The Third Law states that as temperature approaches absolute zero (0 K), the entropy of a perfect crystalline substance tends to zero. This means disorder vanishes at absolute zero. The First Law (option B) is about energy conservation, the Second Law (option C) is about entropy increase and spontaneous direction of heat, and Carnot’s theorem (option D) also comes under the Second Law.
37. Which of the following statements about internal energy is correct?
ⓐ. It is equal to kinetic energy of the system only
ⓑ. It is a state function dependent only on temperature
ⓒ. It includes both microscopic kinetic and potential energies of particles
ⓓ. It is equal to the product of pressure and volume always
Correct Answer: It includes both microscopic kinetic and potential energies of particles
Explanation: Internal energy represents the total microscopic energy of a system due to molecular motion (kinetic) and intermolecular forces (potential). It is a state function depending on state variables like temperature, pressure, and volume. While in ideal gases internal energy depends only on temperature, in real systems intermolecular forces contribute. Option D describes $PV$, which is not always equal to internal energy.
38. Which law of thermodynamics sets the ultimate limit for the efficiency of heat engines?
ⓐ. Zeroth Law
ⓑ. First Law
ⓒ. Second Law
ⓓ. Third Law
Correct Answer: Second Law
Explanation: The Second Law of Thermodynamics states that no heat engine can be 100% efficient because some heat is always rejected to a sink. This limit is quantified by Carnot efficiency, $\eta = 1 – \frac{T_C}{T_H}$. The First Law ensures energy balance, but it does not impose restrictions on direction or feasibility. The Zeroth and Third Laws define temperature and absolute zero but do not determine efficiency limits.
39. Which property is extensive in thermodynamics?
ⓐ. Temperature
ⓑ. Pressure
ⓒ. Volume
ⓓ. Density
Correct Answer: Volume
Explanation: Extensive properties depend on the amount of matter in the system. Volume, internal energy, enthalpy, and entropy are extensive. Intensive properties, like temperature, pressure, and density, do not depend on system size. For example, doubling the amount of gas doubles the volume but leaves temperature and pressure unchanged (if conditions remain same).
40. The concept of reversibility in thermodynamics refers to:
ⓐ. A process that takes infinite time and can be exactly reversed
ⓑ. A process that is very fast and cannot be controlled
ⓒ. A process where heat always flows from cold to hot
ⓓ. A process that violates the First Law
Correct Answer: A process that takes infinite time and can be exactly reversed
Explanation: A reversible process is an idealized concept where the system changes state through infinitesimal steps and can return to the initial state without leaving any effect on surroundings. Real processes are always irreversible due to friction, heat losses, and entropy generation. Options B, C, and D are incorrect because they contradict the definitions of thermodynamics or physical laws.
41. What does thermal equilibrium mean for two bodies in contact?
ⓐ. They have the same pressure
ⓑ. They have the same temperature
ⓒ. They have the same volume
ⓓ. They exchange heat continuously
Correct Answer: They have the same temperature
Explanation: Thermal equilibrium occurs when two bodies in thermal contact no longer exchange heat. This condition is achieved when both bodies have the same temperature. Heat transfer only happens when there is a temperature difference, and stops once equilibrium is reached. Pressure and volume may differ, but they are not the defining condition for thermal equilibrium.
42. If body A is in thermal equilibrium with body B, and body B is in thermal equilibrium with body C, then which law applies?
ⓐ. First Law of Thermodynamics
ⓑ. Second Law of Thermodynamics
ⓒ. Zeroth Law of Thermodynamics
ⓓ. Third Law of Thermodynamics
Correct Answer: Zeroth Law of Thermodynamics
Explanation: The Zeroth Law establishes the transitive property of thermal equilibrium: if A is in equilibrium with B, and B is in equilibrium with C, then A is in equilibrium with C. This law is fundamental to the definition of temperature and allows the use of thermometers.
43. Which physical property equalizes between two systems in thermal equilibrium?
ⓐ. Temperature
ⓑ. Density
ⓒ. Volume
ⓓ. Entropy
Correct Answer: Temperature
Explanation: Temperature is the physical property that becomes the same when systems reach thermal equilibrium. Density, volume, or entropy may change during energy exchange, but they are not the defining parameters for equilibrium.
44. A hot cup of tea placed in a cooler room eventually cools down. When does thermal equilibrium occur?
ⓐ. When the tea becomes colder than the room
ⓑ. When the tea becomes warmer than the room
ⓒ. When the tea and the room air reach the same temperature
ⓓ. When the tea stops evaporating
Correct Answer: When the tea and the room air reach the same temperature
Explanation: Heat flows from the tea (hot body) to the air (cooler body) until both reach the same temperature. At that point, no net heat exchange occurs, meaning thermal equilibrium is achieved. Evaporation may still occur, but it does not affect the definition of thermal equilibrium.
45. What is the condition for no net heat transfer between two systems?
ⓐ. They are in thermal equilibrium
ⓑ. They have the same mass
ⓒ. They have the same volume
ⓓ. They have the same density
Correct Answer: They are in thermal equilibrium
Explanation: Heat transfer requires a temperature difference. When systems have the same temperature, they are in thermal equilibrium, and no net heat flow occurs. Mass, volume, or density equality does not guarantee equilibrium if temperatures differ.
46. Which instrument operates on the principle of thermal equilibrium?
ⓐ. Barometer
ⓑ. Thermometer
ⓒ. Hygrometer
ⓓ. Galvanometer
Correct Answer: Thermometer
Explanation: A thermometer measures temperature by coming into thermal equilibrium with the body. The thermometer’s fluid or sensor attains the same temperature as the body, and the scale reflects that value. A barometer measures pressure, a hygrometer humidity, and a galvanometer current, none of which are based on thermal equilibrium.
47. Two bodies at different temperatures are brought into thermal contact. Which direction does heat flow initially?
ⓐ. From colder to hotter
ⓑ. From hotter to colder
ⓒ. Both directions equally
ⓓ. Heat does not flow at all
Correct Answer: From hotter to colder
Explanation: Heat always flows spontaneously from a higher temperature body to a lower temperature one, as stated by the Second Law of Thermodynamics. This continues until both bodies attain the same temperature, i.e., thermal equilibrium. Heat never flows naturally from cold to hot.
48. Why is the concept of thermal equilibrium important in defining temperature?
ⓐ. Because temperature is measured by pressure changes
ⓑ. Because it allows comparing temperatures of different systems without direct contact
ⓒ. Because it avoids the need to measure energy directly
ⓓ. Because it proves that entropy always increases
Correct Answer: Because it allows comparing temperatures of different systems without direct contact
Explanation: The Zeroth Law implies that if two systems are separately in equilibrium with a third system (like a thermometer), they are in equilibrium with each other. This provides a reliable and universal way to compare and measure temperatures.
49. A thermometer placed in boiling water reads 100 °C. Why does it stop rising after reaching that value?
ⓐ. The thermometer cannot measure above 100 °C
ⓑ. The water and thermometer have reached thermal equilibrium
ⓒ. The pressure prevents further heating
ⓓ. The water loses all its heat instantly
Correct Answer: The water and thermometer have reached thermal equilibrium
Explanation: When immersed in boiling water, the thermometer exchanges heat with the water until both reach the same temperature (100 °C at 1 atm pressure). At that point, no further heat exchange occurs, and the thermometer reading stabilizes, showing thermal equilibrium.
50. When an ice cube is placed in a glass of water, the system reaches thermal equilibrium when:
ⓐ. The ice completely disappears
ⓑ. The water becomes as cold as ice instantly
ⓒ. Both ice and water attain the same final temperature
ⓓ. The ice stops floating
Correct Answer: Both ice and water attain the same final temperature
Explanation: Heat flows from water (hotter) to ice (colder) until both attain the same temperature. This final temperature is the equilibrium temperature. The ice may or may not completely melt, depending on heat available, but equilibrium is achieved once temperatures equalize.
51. Which of the following is a necessary condition for achieving thermal equilibrium between two bodies?
ⓐ. They must have the same mass
ⓑ. They must be in thermal contact
ⓒ. They must have equal volume
ⓓ. They must be made of the same material
Correct Answer: They must be in thermal contact
Explanation: Thermal equilibrium requires physical contact (direct or indirect) that allows heat exchange between bodies. Without thermal contact, there can be no energy transfer. Mass, volume, or material type do not determine equilibrium directly, as bodies of different masses or materials can still reach the same temperature.
52. Two bodies with masses $m_1$ and $m_2$, specific heats $c_1$ and $c_2$, and initial temperatures $T_1$ and $T_2$, are brought in thermal contact. The final equilibrium temperature $T_f$ is given by:
ⓐ. $T_f = \frac{T_1 + T_2}{2}$
ⓑ. $T_f = \frac{m_1 c_1 T_1 + m_2 c_2 T_2}{m_1 c_1 + m_2 c_2}$
ⓒ. $T_f = m_1 c_1 + m_2 c_2$
ⓓ. $T_f = T_1 – T_2$
Correct Answer: $T_f = \frac{m_1 c_1 T_1 + m_2 c_2 T_2}{m_1 c_1 + m_2 c_2}$
Explanation: Conservation of energy applies: heat lost by the hotter body equals heat gained by the cooler body. Thus,$$m_1 c_1 (T_1 – T_f) = m_2 c_2 (T_f – T_2),$$
solving gives the weighted average formula in option B. Options A, C, and D ignore mass and specific heat contributions, making them incorrect.
53. Which condition is essential for a thermometer to correctly measure body temperature?
ⓐ. It must reach mechanical equilibrium
ⓑ. It must reach thermal equilibrium with the body
ⓒ. It must have the same mass as the body
ⓓ. It must be made of mercury only
Correct Answer: It must reach thermal equilibrium with the body
Explanation: A thermometer shows accurate readings only after attaining the same temperature as the body under measurement. This requires sufficient thermal contact and time for heat transfer. The material (mercury, alcohol, digital sensors) does not matter as long as equilibrium is achieved.
54. A 200 g block of copper at $100^\circ C$ is placed in 100 g of water at $30^\circ C$. If the specific heat of copper is $0.39 \, \text{J/g}^\circ C$ and water is $4.18 \, \text{J/g}^\circ C$, the equilibrium temperature $T_f$ is approximately:
ⓐ. $32^\circ C$
ⓑ. $36^\circ C$
ⓒ. $40^\circ C$
ⓓ. $50^\circ C$
Correct Answer: $36^\circ C$
Explanation: Heat lost by copper = Heat gained by water:$$m_{Cu} c_{Cu} (100 – T_f) = m_w c_w (T_f – 30).$$
$$200 \times 0.39 (100 – T_f) = 100 \times 4.18 (T_f – 30).$$
$$78(100 – T_f) = 418 (T_f – 30).$$
$$7800 – 78T_f = 418T_f – 12540.$$
$$20340 = 496T_f \Rightarrow T_f \approx 36.6^\circ C.$$
Hence, option B is correct.
55. For thermal equilibrium to be established, the heat transfer must continue until:
ⓐ. The internal energy of both bodies is equal
ⓑ. The heat capacities of both bodies are equal
ⓒ. Both bodies attain the same final temperature
ⓓ. The masses of both bodies are equal
Correct Answer: Both bodies attain the same final temperature
Explanation: The defining condition of thermal equilibrium is equal temperature. Internal energies and heat capacities may differ depending on material and size, but equilibrium means no net heat flow, achieved only when temperatures equalize.
56. If a hot metal rod is dipped in water, which factor does NOT affect the final equilibrium temperature?
ⓐ. Mass of water
ⓑ. Specific heat capacity of metal
ⓒ. Initial temperature difference
ⓓ. Shape of the metal rod
Correct Answer: Shape of the metal rod
Explanation: The equilibrium temperature depends on the heat balance equation involving masses, specific heats, and initial temperatures. The rod’s shape does not matter because energy exchange depends only on thermal properties, not geometry, unless heat loss to surroundings is considered.
57. Two objects in thermal contact are said to be in equilibrium when:
ⓐ. Net heat flow between them is zero
ⓑ. Their masses are equal
ⓒ. They contain the same amount of energy
ⓓ. Their specific heats are the same
Correct Answer: Net heat flow between them is zero
Explanation: At equilibrium, no further heat is exchanged between the objects, meaning they are at the same temperature. Mass, energy content, or specific heat equality is not required.
58. A piece of iron of mass 500 g at $80^\circ C$ is dropped into 200 g of water at $25^\circ C$. If $c_{Fe} = 0.45 \, \text{J/g}^\circ C$ and $c_{w} = 4.18 \, \text{J/g}^\circ C$, the equilibrium temperature is closest to:
ⓐ. $30^\circ C$
ⓑ. $35^\circ C$
ⓒ. $40^\circ C$
ⓓ. $45^\circ C$
Correct Answer: $40^\circ C$
Explanation: Using heat balance:$$m_{Fe} c_{Fe} (80 – T_f) = m_w c_w (T_f – 25).$$
$$500 \times 0.45 (80 – T_f) = 200 \times 4.18 (T_f – 25).$$
$$225 (80 – T_f) = 836 (T_f – 25).$$
$$18000 – 225T_f = 836T_f – 20900.$$
$$38900 = 1061T_f \Rightarrow T_f \approx 36.7^\circ C.$$
Thus, the closest answer is $40^\circ C$.
59. Which condition ensures accurate temperature measurement using a thermometer?
ⓐ. Large thermal mass of the thermometer compared to the body
ⓑ. Very short contact time between thermometer and body
ⓒ. Small thermal capacity of the thermometer relative to the body
ⓓ. No physical contact between thermometer and body
Correct Answer: Small thermal capacity of the thermometer relative to the body
Explanation: A thermometer must have low heat capacity so that its temperature changes quickly without significantly altering the body’s temperature. If its thermal mass is large, it will absorb too much energy, lowering accuracy. Physical contact is mandatory for equilibrium.
60. Which of the following best describes the role of insulation in achieving thermal equilibrium in experiments?
ⓐ. It accelerates heat exchange
ⓑ. It prevents heat loss to surroundings so equilibrium is reached between only the chosen bodies
ⓒ. It equalizes masses of the bodies
ⓓ. It increases the density of the system
Correct Answer: It prevents heat loss to surroundings so equilibrium is reached between only the chosen bodies
Explanation: Insulation ensures that heat exchange occurs only between the objects under consideration, not with the environment. This allows precise determination of equilibrium temperature. Without insulation, external heat losses distort results.
61. Why is temperature measurement important in thermodynamics?
ⓐ. It determines the color of an object
ⓑ. It helps define thermal equilibrium and energy transfer
ⓒ. It only helps in studying motion
ⓓ. It is unrelated to heat flow
Correct Answer: It helps define thermal equilibrium and energy transfer
Explanation: Temperature is a key thermodynamic property used to determine whether two systems are in thermal equilibrium. It also governs the direction of heat flow—heat always flows from higher temperature to lower temperature until equilibrium is achieved.
62. Which law forms the basis of temperature measurement and calibration?
ⓐ. First Law of Thermodynamics
ⓑ. Zeroth Law of Thermodynamics
ⓒ. Second Law of Thermodynamics
ⓓ. Third Law of Thermodynamics
Correct Answer: Zeroth Law of Thermodynamics
Explanation: The Zeroth Law provides the foundation for temperature measurement by establishing that if two systems are in thermal equilibrium with a third, they are in equilibrium with each other. This principle allows thermometers to be calibrated and used reliably.
63. Calibration of thermometers requires reference points. Which two are most commonly used?
ⓐ. Boiling point and freezing point of water
ⓑ. Melting point of iron and copper
ⓒ. Absolute zero and density of water
ⓓ. Room temperature and humidity
Correct Answer: Boiling point and freezing point of water
Explanation: Thermometers are traditionally calibrated using fixed points: the freezing point (0 °C) and boiling point (100 °C) of water at 1 atm pressure. These reference points provide reproducible standards for defining temperature scales.
64. Why is calibration of thermometers necessary?
ⓐ. To reduce the size of the thermometer
ⓑ. To correct errors and ensure accurate temperature readings
ⓒ. To make the thermometer waterproof
ⓓ. To increase the density of the liquid in the thermometer
Correct Answer: To correct errors and ensure accurate temperature readings
Explanation: Manufacturing imperfections can cause deviations in scale readings. Calibration aligns the instrument with standard reference temperatures, ensuring precision in scientific and industrial measurements.
65. A thermometer placed in thermal contact with a body shows a steady reading after some time. What does this indicate?
ⓐ. The thermometer is malfunctioning
ⓑ. The thermometer has reached thermal equilibrium with the body
ⓒ. The thermometer has stopped working
ⓓ. The thermometer is losing heat to the environment
Correct Answer: The thermometer has reached thermal equilibrium with the body
Explanation: A thermometer must first reach thermal equilibrium with the system to accurately indicate its temperature. Once equilibrium is reached, the reading remains steady, reflecting the body’s true temperature.
66. The Celsius scale is calibrated such that:
ⓐ. 0 °C corresponds to boiling of water and 100 °C to freezing of water
ⓑ. 0 °C corresponds to freezing of water and 100 °C to boiling of water
ⓒ. 0 °C corresponds to absolute zero and 100 °C to room temperature
ⓓ. 0 °C corresponds to melting of iron and 100 °C to melting of lead
Correct Answer: 0 °C corresponds to freezing of water and 100 °C to boiling of water
Explanation: The Celsius scale is based on two fixed points at standard atmospheric pressure: freezing point of water (0 °C) and boiling point of water (100 °C). Other options confuse different reference values not used in calibration.
67. Which factor must be avoided to ensure accurate calibration of thermometers?
ⓐ. Standard atmospheric pressure variation
ⓑ. Proper immersion depth in liquid
ⓒ. Heat loss to the environment
ⓓ. All of the above
Correct Answer: All of the above
Explanation: Accurate calibration requires standard conditions. Pressure affects boiling and freezing points, immersion depth affects heat transfer, and heat loss to surroundings can cause errors. Therefore, all factors must be controlled.
68. Why is Kelvin scale preferred in scientific thermodynamics?
ⓐ. It is larger in size
ⓑ. It starts from absolute zero and is an absolute scale
ⓒ. It uses smaller units than Celsius
ⓓ. It is easier to manufacture thermometers in Kelvin
Correct Answer: It starts from absolute zero and is an absolute scale
Explanation: The Kelvin scale is based on absolute zero, where molecular motion ceases. It avoids negative temperatures and directly relates to the laws of thermodynamics, making it the standard for scientific research.
69. A resistance thermometer works on the principle that:
ⓐ. Resistance of a conductor changes with temperature
ⓑ. Volume of liquid expands with temperature
ⓒ. Pressure of gas increases with temperature
ⓓ. Heat capacity changes with temperature
Correct Answer: Resistance of a conductor changes with temperature
Explanation: Resistance thermometers use metals like platinum, whose electrical resistance varies predictably with temperature. By measuring resistance, accurate temperature can be determined after proper calibration.
70. Why is calibration critical in high-precision scientific experiments?
ⓐ. Because errors of even small fractions of degrees can affect results significantly
ⓑ. Because temperature is irrelevant in experiments
ⓒ. Because calibration reduces the size of thermometers
ⓓ. Because calibration prevents heat transfer
Correct Answer: Because errors of even small fractions of degrees can affect results significantly
Explanation: In sensitive experiments like chemical reactions, phase transitions, and engineering processes, even small temperature deviations can alter results. Calibration ensures high accuracy, making measurements reliable and reproducible.
71. What does the Zeroth Law of Thermodynamics state?
ⓐ. Heat cannot flow from cold to hot without work
ⓑ. Energy cannot be created or destroyed
ⓒ. If two systems are each in thermal equilibrium with a third system, then they are in equilibrium with each other
ⓓ. Entropy of a perfect crystal at absolute zero is zero
Correct Answer: If two systems are each in thermal equilibrium with a third system, then they are in equilibrium with each other
Explanation: The Zeroth Law establishes the transitive nature of thermal equilibrium, which is the basis of temperature measurement. Options A and B describe the Second and First Laws, while option D belongs to the Third Law.
72. Why is the Zeroth Law called “zeroth” and not the fourth law?
ⓐ. Because it was discovered before all other laws
ⓑ. Because it was formulated after the other laws but is more fundamental
ⓒ. Because it was a mathematical mistake
ⓓ. Because it deals with zero degrees Celsius
Correct Answer: Because it was formulated after the other laws but is more fundamental
Explanation: The Zeroth Law was formally stated after the First and Second Laws, but it underlies the concept of temperature, making it more fundamental. Therefore, scientists placed it before the First Law in naming.
73. Which practical device relies directly on the Zeroth Law?
ⓐ. Barometer
ⓑ. Thermometer
ⓒ. Calorimeter
ⓓ. Hygrometer
Correct Answer: Thermometer
Explanation: A thermometer works by reaching thermal equilibrium with the body whose temperature is measured. The Zeroth Law guarantees that when both are in equilibrium, they share the same temperature, allowing accurate measurement.
74. Why is the Zeroth Law significant in thermodynamics?
ⓐ. It defines entropy
ⓑ. It provides the foundation for defining and measuring temperature
ⓒ. It explains energy conservation
ⓓ. It restricts the efficiency of engines
Correct Answer: It provides the foundation for defining and measuring temperature
Explanation: The significance of the Zeroth Law lies in establishing temperature as a measurable property. Without it, comparing and calibrating temperatures using thermometers would not be scientifically valid.
75. Which property equalizes when two systems are in thermal equilibrium according to the Zeroth Law?
ⓐ. Mass
ⓑ. Density
ⓒ. Temperature
ⓓ. Pressure
Correct Answer: Temperature
Explanation: The Zeroth Law tells us that temperature is the parameter that equalizes when two systems are in thermal equilibrium. Mass, density, and pressure may differ, but temperature is the defining condition.
76. How does the Zeroth Law ensure consistency in temperature measurement?
ⓐ. By relating heat to work
ⓑ. By ensuring transitivity of thermal equilibrium
ⓒ. By defining entropy
ⓓ. By limiting temperature range
Correct Answer: By ensuring transitivity of thermal equilibrium
Explanation: The Zeroth Law states that if A = B and B = C in terms of thermal equilibrium, then A = C. This transitivity property ensures that temperature is consistent across different systems, allowing universal calibration of thermometers.
77. Two objects, A and B, are in thermal equilibrium. Object B is also in thermal equilibrium with object C. According to the Zeroth Law:
ⓐ. A and C must have the same mass
ⓑ. A and C must have the same temperature
ⓒ. A and C must exchange heat continuously
ⓓ. A and C cannot be compared
Correct Answer: A and C must have the same temperature
Explanation: The Zeroth Law confirms that A and C are also in thermal equilibrium through B. Thus, all three share the same temperature, making comparison and measurement possible.
78. Why is the Zeroth Law crucial for building temperature scales like Celsius and Kelvin?
ⓐ. Because it relates temperature with energy
ⓑ. Because it guarantees a consistent and transitive definition of temperature
ⓒ. Because it defines entropy as zero at absolute zero
ⓓ. Because it provides formulas for energy conservation
Correct Answer: Because it guarantees a consistent and transitive definition of temperature
Explanation: Without the Zeroth Law, there would be no universal basis for comparing temperatures. The law ensures that temperature can be consistently defined and scaled across different systems, enabling Celsius, Fahrenheit, and Kelvin scales.
79. Which of the following is the best example of the Zeroth Law in action?
ⓐ. A hot iron rod cooling down in air
ⓑ. A thermometer showing the temperature of boiling water
ⓒ. A steam engine converting heat to work
ⓓ. Melting of ice into water
Correct Answer: A thermometer showing the temperature of boiling water
Explanation: The thermometer works because it comes into thermal equilibrium with boiling water. Both then share the same temperature, and the thermometer reading reflects that. Other options involve heat transfer or phase change, but not direct measurement of equilibrium.
80. The Zeroth Law is significant because it:
ⓐ. Explains why entropy increases
ⓑ. Provides the theoretical foundation of temperature measurement and thermometry
ⓒ. Defines the conservation of energy principle
ⓓ. Determines the efficiency of Carnot engines
Correct Answer: Provides the theoretical foundation of temperature measurement and thermometry
Explanation: The Zeroth Law is fundamental in thermodynamics because it provides the reasoning for the existence of temperature as a physical quantity and allows thermometers to function. Other options relate to the First and Second Laws, not the Zeroth Law.
81. A thermometer is placed in a liquid at $80^\circ C$. After some time, the thermometer reads $80^\circ C$. What does this indicate according to the Zeroth Law?
ⓐ. The thermometer is broken
ⓑ. The thermometer has reached thermal equilibrium with the liquid
ⓒ. The thermometer has absorbed all heat from the liquid
ⓓ. The thermometer’s mercury stopped expanding
Correct Answer: The thermometer has reached thermal equilibrium with the liquid
Explanation: The Zeroth Law states that when two bodies are in thermal equilibrium, their temperatures are the same. The thermometer and the liquid share the same temperature, and the reading confirms equilibrium.
82. Two bodies A and B, with heat capacities $C_A = 500 \, J/K$ and $C_B = 300 \, J/K$, are initially at $T_A = 350 K$ and $T_B = 300 K$. If they are placed in contact in an isolated system, the final equilibrium temperature is:
ⓐ. 310 K
ⓑ. 320 K
ⓒ. 330 K
ⓓ. 340 K
Correct Answer: 330 K
Explanation: By energy conservation:$$C_A (T_A – T_f) = C_B (T_f – T_B).$$
$$500(350 – T_f) = 300(T_f – 300).$$
$$175000 – 500T_f = 300T_f – 90000.$$
$$265000 = 800T_f \Rightarrow T_f = 331.25 \, K.$$
Thus, closest is 330 K.
83. Why is the Zeroth Law essential for using thermometers in daily life?
ⓐ. Because thermometers work on pressure laws
ⓑ. Because thermometers must be in thermal equilibrium with the body to show correct temperature
ⓒ. Because thermometers increase entropy
ⓓ. Because thermometers conserve energy
Correct Answer: Because thermometers must be in thermal equilibrium with the body to show correct temperature
Explanation: The Zeroth Law ensures that if the thermometer and body are in equilibrium, they have the same temperature. Without this principle, temperature readings would have no physical meaning.
84. A 0.5 kg copper block at $400 K$ is placed in contact with a 1 kg aluminum block at $300 K$. If $c_{Cu} = 390 \, J/kgK$ and $c_{Al} = 900 \, J/kgK$, the final equilibrium temperature is:
ⓐ. 320 K
ⓑ. 340 K
ⓒ. 360 K
ⓓ. 380 K
Correct Answer: 320 K
Explanation: Heat lost by copper = Heat gained by aluminum:$$m_{Cu} c_{Cu} (400 – T_f) = m_{Al} c_{Al} (T_f – 300).$$
$$0.5 \times 390 (400 – T_f) = 1 \times 900 (T_f – 300).$$
$$195 (400 – T_f) = 900 (T_f – 300).$$
$$78000 – 195T_f = 900T_f – 270000.$$
$$348000 = 1095T_f \Rightarrow T_f \approx 318 K.$$
Correct option closest is 320 K.
85. If body A is in thermal equilibrium with body B, and body B with body C, then which parameter is the same for all three according to the Zeroth Law?
ⓐ. Pressure
ⓑ. Volume
ⓒ. Temperature
ⓓ. Heat content
Correct Answer: Temperature
Explanation: The Zeroth Law asserts transitivity of thermal equilibrium. Temperature equalizes across all systems in equilibrium, while pressure, volume, or total heat may differ.
86. A steel ball of mass 0.2 kg at $500 K$ is dropped into 0.5 kg water at $300 K$. If $c_{steel} = 460 \, J/kgK$ and $c_{water} = 4186 \, J/kgK$, the equilibrium temperature is:
ⓐ. 305 K
ⓑ. 310 K
ⓒ. 315 K
ⓓ. 320 K
Correct Answer: 310 K
Explanation: Heat lost by steel = Heat gained by water:$$0.2 \times 460 (500 – T_f) = 0.5 \times 4186 (T_f – 300).$$
$$92(500 – T_f) = 2093(T_f – 300).$$
$$46000 – 92T_f = 2093T_f – 627900.$$
$$673900 = 2185T_f \Rightarrow T_f \approx 308.5 K.$$
Closest option is 310 K.
87. Which of the following best illustrates the significance of the Zeroth Law?
ⓐ. A thermometer measuring body temperature
ⓑ. A piston compressing gas
ⓒ. A steam engine converting heat into work
ⓓ. Ice melting into water
Correct Answer: A thermometer measuring body temperature
Explanation: The thermometer and the body must be in thermal equilibrium. Once achieved, the thermometer shows the body’s temperature. This is a direct application of the Zeroth Law.
88. Two objects with heat capacities $C_1 = 100 \, J/K$ and $C_2 = 200 \, J/K$ are at 500 K and 300 K respectively. What is the final equilibrium temperature?
ⓐ. 340 K
ⓑ. 360 K
ⓒ. 380 K
ⓓ. 400 K
Correct Answer: 360 K
Explanation: By energy conservation:$$C_1 (500 – T_f) = C_2 (T_f – 300).$$
$$100(500 – T_f) = 200(T_f – 300).$$
$$50000 – 100T_f = 200T_f – 60000.$$
$$110000 = 300T_f \Rightarrow T_f = 366.7 K.$$
Closest is 360 K.
89. What is the main reason the Zeroth Law is foundational in thermodynamics?
ⓐ. It explains why entropy increases
ⓑ. It gives physical meaning to temperature and enables its measurement
ⓒ. It defines conservation of energy
ⓓ. It restricts Carnot efficiency
Correct Answer: It gives physical meaning to temperature and enables its measurement
Explanation: The Zeroth Law ensures temperature is a consistent, transitive property, allowing instruments like thermometers to function and providing the foundation for all thermodynamic studies.
90. A 1 kg block of iron at 400 K and a 2 kg block of water at 300 K are placed together in an insulated system. If $c_{iron} = 450 \, J/kgK$ and $c_{water} = 4186 \, J/kgK$, the equilibrium temperature is:
ⓐ. 345 K
ⓑ. 330 K
ⓒ. 315 K
ⓓ. 305 K
Correct Answer: 305 K
Explanation: Heat lost by iron = Heat gained by water:$$1 \times 450 (400 – T_f) = 2 \times 4186 (T_f – 300).$$
$$450(400 – T_f) = 8372(T_f – 300).$$
$$180000 – 450T_f = 8372T_f – 2511600.$$
$$2691600 = 8822T_f \Rightarrow T_f \approx 305 K.$$
91. On the Celsius scale, what are the two fixed reference points traditionally used for calibration?
ⓐ. Melting point of iron and boiling point of mercury
ⓑ. Freezing point and boiling point of water at 1 atm
ⓒ. Absolute zero and critical temperature of oxygen
ⓓ. Room temperature and freezing point of alcohol
Correct Answer: Freezing point and boiling point of water at 1 atm
Explanation: The Celsius scale is defined by two fixed points at standard atmospheric pressure: 0 °C as the freezing point of water and 100 °C as the boiling point of water. These reproducible points allow consistent calibration of thermometers.
92. Which of the following correctly converts 0 °C into Fahrenheit?
ⓐ. 32 °F
ⓑ. 0 °F
ⓒ. 273 °F
ⓓ. –40 °F
Correct Answer: 32 °F
Explanation: The conversion formula is $F = \frac{9}{5}C + 32$. Substituting $C = 0$:$$F = \frac{9}{5}(0) + 32 = 32^\circ F.$$
Thus, 0 °C corresponds to 32 °F.
93. The Kelvin scale is defined by which zero reference point?
ⓐ. Freezing point of water
ⓑ. Absolute zero
ⓒ. Boiling point of mercury
ⓓ. Melting point of ice at 1 atm
Correct Answer: Absolute zero
Explanation: The Kelvin scale is an absolute temperature scale starting at absolute zero (0 K), the point where all molecular motion theoretically ceases. It avoids negative values and is the SI unit of temperature.
94. Convert $100^\circ C$ into Kelvin.
ⓐ. 100 K
ⓑ. 212 K
ⓒ. 273 K
ⓓ. 373 K
Correct Answer: 373 K
Explanation: The relation between Celsius and Kelvin is:$$K = C + 273.15.$$
So, $100 + 273.15 = 373.15 \, K$. Rounded, the correct answer is 373 K.
95. Which temperature is the same numerical value in both Celsius and Fahrenheit scales?
ⓐ. 0 °
ⓑ. –40 °
ⓒ. 100 °
ⓓ. 212 °
Correct Answer: –40 °
Explanation: To find the intersection, solve $C = \frac{5}{9}(F – 32)$ with $C = F$.$$C = \frac{5}{9}(C – 32).$$
$$9C = 5C – 160.$$
$$4C = -160 \Rightarrow C = -40.$$
Hence, –40 °C = –40 °F.
96. Convert normal human body temperature $98.6^\circ F$ into Celsius.
ⓐ. 37 °C
ⓑ. 40 °C
ⓒ. 36 °C
ⓓ. 100 °C
Correct Answer: 37 °C
Explanation: The formula is $C = \frac{5}{9}(F – 32)$. Substituting $F = 98.6$:$$C = \frac{5}{9}(98.6 – 32) = \frac{5}{9}(66.6) = 37^\circ C.$$
Thus, 98.6 °F corresponds to 37 °C.
97. Which statement correctly describes the Fahrenheit scale?
ⓐ. 0 °F is the freezing point of water and 100 °F is the boiling point
ⓑ. 32 °F is the freezing point of water and 212 °F is the boiling point at 1 atm
ⓒ. 0 °F is absolute zero
ⓓ. 100 °F is equal to 0 °C
Correct Answer: 32 °F is the freezing point of water and 212 °F is the boiling point at 1 atm
Explanation: The Fahrenheit scale uses 32 °F and 212 °F as reference points at 1 atm. The interval is divided into 180 equal parts, unlike Celsius which divides into 100 equal parts.
98. Convert absolute zero (0 K) into Celsius and Fahrenheit respectively.
ⓐ. –273 °C and –459 °F
ⓑ. –273 °C and 0 °F
ⓒ. 0 °C and 32 °F
ⓓ. –100 °C and –200 °F
Correct Answer: –273 °C and –459 °F
Explanation: From Kelvin to Celsius: $C = K – 273.15$. For $ K = 0$, $ C = -273.15^\circ C$.
Then to Fahrenheit: $ F = \frac{9}{5}C + 32 = \frac{9}{5}(-273.15) + 32 \approx -459.67^\circ F$.
99. Convert $25^\circ C$ into Fahrenheit.
ⓐ. 75 °F
ⓑ. 77 °F
ⓒ. 100 °F
ⓓ. 273 °F
Correct Answer: 77 °F
Explanation: Using $F = \frac{9}{5}C + 32$:$$F = \frac{9}{5}(25) + 32 = 45 + 32 = 77^\circ F.$$
Thus, 25 °C corresponds to 77 °F.
100. Why is Kelvin preferred in scientific thermodynamics over Celsius or Fahrenheit?
ⓐ. It uses smaller divisions
ⓑ. It starts from absolute zero and avoids negative temperatures
ⓒ. It is easier to convert into Fahrenheit
ⓓ. It is based on human body temperature
Correct Answer: It starts from absolute zero and avoids negative temperatures
Explanation: The Kelvin scale begins at absolute zero (0 K), the fundamental thermodynamic limit. This makes calculations involving energy, entropy, and laws of thermodynamics straightforward, as negative temperatures are avoided.
Welcome to Class 11 Physics MCQs – Chapter 12: Thermodynamics (Part 1). This page is a chapter-wise question bank for the NCERT/CBSE Class 11 Physics syllabus—built for quick revision and exam speed. Practice MCQs / objective questions / Physics quiz items with solutions and explanations, ideal for CBSE Boards, JEE Main, NEET, competitive exams, and Board exams.
These MCQs are suitable for international competitive exams—physics concepts are universal.
Navigation & pages: The full chapter has 500 MCQs in 5 parts (100 + 100 + 100 + 100 + 100). Part 1 contains 100 MCQs split across 10 pages—you’ll see 10 questions per page. Use the page numbers above to view the remaining questions.
What you will learn & practice
- Introduction to Thermodynamics and thermal equilibrium
- Zeroth Law (temperature as a state variable, transitive equilibrium)
- Heat, internal energy, and work (sign conventions, path vs state)
- First Law of Thermodynamics and specific heat capacity
- State variables & equations of state (ideal gas model—overview)
- Thermodynamic processes: isothermal, adiabatic, isobaric, isochoric, cyclic
- Heat engines, refrigerators, and heat pumps (efficiency, COP)
- Second Law: Kelvin–Planck & Clausius statements; reversible vs irreversible
- Carnot engine and entropy (qualitative + basic relations)
- Maxwell’s relations (intro, significance)
How this practice works
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The full chapter includes 500 solved multiple-choice questions in 5 parts. This page (Part 1) gives the first 100 MCQs with answers and explanations to build your foundations. Explore more with: Class 11 Physics – Chapter Index, Class 11 – Subject Index, All Classes – MCQ Library.
- 👉 Total MCQs in this chapter: 500 (100 × 5 parts)
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FAQs on Thermodynamics ▼
▸ What are Thermodynamics MCQs in Class 11 Physics?
Thermodynamics MCQs are multiple-choice questions from Chapter 12 of NCERT Class 11 Physics. They include questions on the laws of thermodynamics, heat, work, internal energy, and entropy to test both conceptual and numerical understanding.
▸ How many Thermodynamics MCQs are available in total?
There are a total of 500 MCQs from Chapter 12 Thermodynamics. They are divided into 5 sets of 100 questions each for systematic practice.
▸ Are these MCQs useful for NCERT and CBSE board exams?
Yes, these Thermodynamics MCQs are strictly based on NCERT/CBSE Class 11 Physics syllabus and are very useful for Class tests, school exams, and state board examinations.
▸ Are Thermodynamics MCQs important for JEE and NEET?
Yes, this chapter is extremely important for JEE and NEET. Numerical problems on laws of thermodynamics, heat engines, and entropy are frequently asked in competitive exams.
▸ Do these MCQs include correct answers and explanations?
Yes, every Thermodynamics MCQ comes with the correct answer and explanations. This helps students not only solve questions but also understand the concept behind each solution.
▸ Who should practice Thermodynamics MCQs?
These MCQs are ideal for Class 11 students, CBSE/NCERT learners, and aspirants of JEE, NEET, NDA, UPSC, and other competitive exams that include Physics.
▸ Can I practice Thermodynamics MCQs online for free?
Yes, all Thermodynamics MCQs on GK Aim are available online for free. They can be practiced anytime using mobile, tablet, or desktop devices.
▸ Are these MCQs helpful for quick revision before exams?
Yes, practicing these MCQs regularly helps in quick revision, strengthens memory recall, and boosts exam performance in practice tests by improving accuracy and speed.
▸ Do these MCQs cover both basic and advanced concepts?
Yes, the Thermodynamics MCQs cover the basics like heat, work, and internal energy as well as advanced topics like entropy, Maxwell’s relations, and thermodynamic potentials.
▸ Why are the 500 Thermodynamics MCQs divided into 5 parts?
The MCQs are divided into 5 sets to make practice more organized and manageable, helping students build concepts step by step without feeling overloaded.
▸ Which subtopics are included in Thermodynamics MCQs?
The MCQs include subtopics like the Zeroth Law of Thermodynamics, First Law of Thermodynamics, Second Law, entropy, heat engines, Carnot cycle, and Maxwell’s relations.
▸ Are numerical problems included in these MCQs?
Yes, the Thermodynamics MCQs contain both conceptual and numerical questions, such as calculations of efficiency, entropy change, and work done in thermodynamic processes.
▸ Can teachers and coaching institutes use these Thermodynamics MCQs?
Yes, teachers and coaching centers can use these MCQs as ready-made assignments, quizzes, and practice tests for students preparing for board and competitive exams.
▸ Are these MCQs mobile-friendly?
Yes, the Thermodynamics MCQs pages are optimized for smartphones and tablets, making it easy for students to practice anywhere, anytime.
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Yes, you can download these Thermodynamics MCQs in PDF format for offline use. Please visit our website shop.gkaim.com