Thermodynamics Basics & Fundamentals-100 Mcq’s
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The SI unit of density is:
Explanation: Density is mass per unit volume, so its unit is kilograms per cubic meter (kg/m³) in SI.
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What is the dimension of pressure?
Explanation: Pressure (force/area) has dimensions of [M L T⁻²] ÷ [L²] = [M L⁻¹ T⁻²], as in Pascal.
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The unit of work in thermodynamics is:
Explanation: Work, like energy, is measured in Joules (J), equivalent to Newton-meter (N·m) in SI units.
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What is the dimension of volume?
Explanation: Volume is length cubed, so its dimension is [L³], measured in cubic meters (m³) in SI
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The SI unit of thermodynamic entropy is:
Explanation: Entropy measures energy per temperature, so its unit is Joules per Kelvin (J/K) in SI.
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What is the dimension of power in thermodynamics?
Explanation: Power (energy/time) has dimensions of [M L² T⁻²] ÷ [T] = [M L² T⁻³], as in Watts (J/s).
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The unit of specific heat capacity is:
Explanation: Specific heat capacity is energy per unit mass per unit temperature, so its unit is Joules per kilogram per Kelvin.
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What is the dimension of temperature?
Explanation: Temperature is a fundamental dimension [θ], measured in Kelvin (K) in SI units, not derived from mass, length, or time.
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The SI unit of pressure is:
Explanation: Pressure is force per unit area, measured in Pascal (Pa), equivalent to N/m² in SI units
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What is the dimension of energy in thermodynamics?
Explanation: Energy (e.g., Joule) has dimensions of mass [M], length squared [L²], and time inverse squared [T⁻²], as in force × distance
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Quasi-static processes are important because they:
Explanation: Quasi-static processes have well-defined properties, making them easier to analyze in thermodynamic calculations.
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Which system undergoes a quasi-static process?
Explanation: Slow heating allows the system to adjust gradually, maintaining near-equilibrium, typical of quasi-static processes.
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A quasi-static process is often:
Explanation: Quasi-static processes are idealized as reversible since they occur slowly, minimizing energy losses.
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Which condition ensures a process is quasi-static?
Explanation: Quasi-static processes involve small, gradual changes, keeping the system near equilibrium at every step.
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In a quasi-static isothermal process, what remains constant?
Explanation: An isothermal process keeps temperature constant, and in a quasi-static case, it occurs slowly to maintain equilibrium.
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A non-quasi-static process is typically:
Explanation: Non-quasi-static processes, like rapid expansion, deviate from equilibrium and are often irreversible.
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Why are quasi-static processes idealized?
Explanation: In quasi-static processes, properties like pressure and temperature are uniform at each step, ideal for analysis.
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Which is an example of a quasi-static process?
Explanation: Slow compression allows the gas to adjust gradually, maintaining near-equilibrium conditions.
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In a quasi-static process, the system:
Explanation: The system remains infinitesimally close to equilibrium, allowing properties like temperature and pressure to be uniform.
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What is a quasi-static process?
Explanation: A quasi-static process happens slowly, keeping the system close to equilibrium, with well-defined properties at each step
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Thermodynamic equilibrium implies:
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Which system is likely in thermodynamic equilibrium?
Explanation: A sealed system with constant temperature, pressure, and no changes is in thermodynamic equilibrium.
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If a system has different temperatures in different parts, it lacks:
Explanation: Thermal equilibrium requires uniform temperature throughout the system.
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A gas in a closed container reaches thermodynamic equilibrium when:
Explanation: Uniform temperature (thermal equilibrium) is a key condition for thermodynamic equilibrium, along with pressure and composition stability.
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Which is NOT a condition for thermodynamic equilibrium?
Explanation: Thermodynamic equilibrium requires no energy transfer (e.g., heat or work) as properties are stable
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A sealed thermos with water at 25°C is in:
Explanation: If temperature, pressure, and composition are uniform and constant, the system is in thermodynamic equilibrium.
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Chemical equilibrium in a system means:
Explanation: Chemical equilibrium is achieved when no chemical reactions occur, and the composition remains stable.
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A system in mechanical equilibrium has:
Explanation: Mechanical equilibrium occurs when the system has uniform pressure, with no net forces causing motion
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Which condition is required for thermal equilibrium?
Explanation: Thermal equilibrium means the system has the same temperature throughout, with no heat flow.
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What is thermodynamic equilibrium?
Explanation: In thermodynamic equilibrium, properties like temperature and pressure stay constant with no tendency to change.
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A steam power plant operates on:
Explanation: A steam power plant uses a cycle (e.g., Rankine cycle) where the working fluid undergoes repeated processes to produce work.
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Which is true for a thermodynamic process?
Explanation: A process is a change from one state to another, e.g., expanding a gas from high to low pressure.
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The path of a process determines:
Explanation: The path describes the sequence of states during a process, like whether it’s isothermal or adiabatic.
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In a thermodynamic cycle, the system:
Explanation: A cycle brings the system back to its starting state after a series of processes, e.g., in a heat engine.
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An isothermal process involves:
Explanation: An isothermal process occurs at constant temperature, like compressing a gas while maintaining its temperature.
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Which property is NOT used to define a state?
Explanation: State is defined by properties like temperature, pressure, and volume. Work is a path function, not a state property.
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Which of the following is an example of a cycle?
Explanation: A cycle involves processes that return the system to its initial state, like in a refrigeration system.
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A thermodynamic process is:
Explanation: A process is a transition from one state to another, e.g., heating a gas to increase its pressure
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The path in thermodynamics refers to:
Explanation: The path is the series of states a system goes through during a change, like isothermal compression of a gas.
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What defines a thermodynamic state?
Explanation: A state is defined by properties like temperature, pressure, and volume at a specific point, e.g., water at 25°C and 1 atm.
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In a thermodynamic process, which property’s change is path-independent?
Explanation: Internal energy is a point function, so its change depends only on initial and final states, not the path.
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Which pair includes only point functions?
Explanation: Pressure and temperature are point functions, defined by the state. Heat and work are path functions
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Why is heat considered a path function?
Explanation: Heat depends on the process (e.g., different heat in isothermal vs. isobaric processes), so it’s a path function.
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The entropy of a system is:
Explanation: Entropy depends only on the system’s state, making it a point function, unlike work or heat.
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Which is NOT a point function?
Explanation: Heat transfer is a path function, varying with the process. Entropy, temperature, and specific volume are point functions.
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During gas expansion, which remains a point function?
Explanation: Pressure is a point function, with a definite value at any state, independent of the expansion process.
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Which property varies with the thermodynamic process?
Explanation: Work is a path function, as its value depends on the process (e.g., isothermal vs. adiabatic compression).
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A property with a definite value at a system’s state is:
Explanation: Point functions, like temperature or density, are defined by the system’s state and measurable at a single point.
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Which of these is a path function?
Explanation: Heat is a path function because its value depends on the process (e.g., how energy is transferred), not just the state.
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What defines a point function in thermodynamics?
Explanation: Point functions, like temperature or pressure, have a fixed value at a specific state, regardless of the process taken
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Which pair consists of only intensive properties?
Explanation: Density and temperature are intensive, as they do not depend on the amount of matter. The other pairs include extensive properties like mass, volume, weight, energy, length, and surface area
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If the mass of a sample doubles, what happens to its density?
Explanation: Density (mass/volume) is intensive. If both mass and volume double proportionally, density stays constant for the same substance.
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Which property is useful for comparing two different samples of the same substance?
Explanation: Melting point is intensive, so it remains the same for any sample of a substance (e.g., ice melts at 0°C), making it ideal for comparison.
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The volume of a gas in a container is:
Explanation: Volume is extensive because it increases with the amount of gas. More gas in the container means a larger volume.
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Which of the following is NOT an extensive property?
Explanation: Pressure is an intensive property, as it does not depend on the amount of matter. Energy, weight, and surface area scale with the sample size.
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If you divide a sample of water into two equal parts, which property remains unchanged?
Explanation: Specific heat is an intensive property, staying constant regardless of the sample size. Mass and volume halve when the sample is divided.
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Which property would help identify a material regardless of its size?
Explanation: Density is an intensive property, unique to a material (e.g., gold has a specific density), and does not vary with sample size.
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The temperature of a substance is an example of:
Explanation: Temperature is intensive because it does not change with the amount of substance. A small or large sample of water at 25°C has the same temperature.
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Which of the following is an extensive property?
Explanation: Extensive properties, like mass or volume, depend on the amount of matter in the sample. More matter means a larger value.
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What is an intensive property of matter?
Explanation: Intensive properties, like density or temperature, remain the same regardless of the sample size or amount of matter.
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A boundary that moves during expansion or compression is called:
Explanation: In piston-cylinder systems, the piston moves — making it a movable boundary.
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In thermodynamics, boundaries are selected based on:
Explanation: Boundaries can be imagined based on how the system is defined in a given scenario.
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The surroundings in a steam engine cycle would be:
Explanation: Everything outside the system (e.g., steam engine), like the atmosphere, is considered surroundings.
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A boundary that allows no interaction of any kind is:
Explanation: An isolated system has boundaries that prevent energy and matter exchange.
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Which of the following boundaries allows heat transfer?
Explanation: Diathermic boundaries allow heat exchange; adiabatic ones do not.
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A boundary that allows energy but not matter to pass is:
Explanation: Closed systems allow energy (like heat/work) to pass but not matter.
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The system and surroundings together form the:
Explanation: System + surroundings = Universe, in thermodynamic terms.
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The interaction between the system and surroundings happens through the:
Explanation: All energy or matter exchange between system and surroundings occurs across the boundary.
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The boundary in a thermodynamic system:
Explanation: A boundary can be fixed/movable and real or imaginary depending on the problem.
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In thermodynamics, the area outside the system is called:
Explanation: Everything external to the system that can interact with it is called the surroundings.
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In which system is only heat or work exchanged but not matter?
Explanation: In a closed system, energy crosses the boundary but the matter remains fixed.
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Which one of the following is NOT a feature of a closed system?
Explanation: A closed system does not allow mass to flow — only energy crosses.
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A piston-cylinder arrangement with no heat loss and fixed mass is:
Explanation: No mass transfer but energy in the form of work/heat can move — closed system.
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Which system applies to a human being breathing air?
Explanation: A human body exchanges both energy and matter with the environment — an open system.
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Which one of the following represents an isolated system?
Explanation: A perfectly insulated thermos prevents both heat and matter transfer — isolated in theory.
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A thermos bottle attempts to behave like:
Explanation: Heat and vapor (matter) can leave the pot — making it an open system.
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Which of these is the best example of an open system?
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An isolated system is best described as:
Explanation: An isolated system does not interact with surroundings — no matter or energy crosses the boundary.
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Which of the following is a closed system?
Explanation: A closed system doesn’t allow matter exchange, only energy like heat can pass.
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An open system allows:
Explanation: In open systems, both matter and energy can enter or leave the system.
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Thermodynamics is indirectly applied in which of the following?
Batteries involve chemical reactions with energy conversion — a thermodynamic process.
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HVAC systems are designed using:
Heating, Ventilation, and Air Conditioning (HVAC) systems use heat transfer and energy balance concepts
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In the aerospace industry, thermodynamics helps in:
Thermodynamics is used to improve fuel efficiency in jet engines and rockets.
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A thermal power plant operates based on which thermodynamic cycle?
The Rankine cycle is used in thermal power plants for steam turbine operation.
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Thermodynamics is useful in the refrigeration industry for
Refrigeration systems transfer heat from a cold space to a warmer one.
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Which of the following uses thermodynamics in energy conversion?
All convert natural energy to usable forms using thermodynamic concepts.
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Thermodynamic principles help improve
One major goal in engineering is to use thermodynamics to improve energy efficiency.
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In which area of daily life is thermodynamics applied?
Cooking involves heat transfer; cars run on engines based on thermodynamic cycles.
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Thermodynamics is essential in the design of:
Explanation: Power generation and engines rely on energy conversion principles of thermodynamics.
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Which branch of engineering uses thermodynamics the most?
Explanation: Mechanical engineering heavily uses thermodynamics for systems like engines, turbines, and HVAC.
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Q10. Which of the following best defines thermodynamics?
Explanation: Thermodynamics is fundamentally about energy, heat, and their relation with matter.
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Q9. Thermodynamics plays a key role in:
Explanation: Power cycles are designed based on thermodynamic principles.
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Q8. The study of thermodynamics can help design:
Explanation: Thermodynamics is essential in designing engines and energy systems
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Q7. The science of thermodynamics is mostly related to:
Explanation: Thermodynamics is a core part of mechanical, chemical, and physics-based engineering.
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Q6. Which of the following industries relies heavily on thermodynamics?
Explanation: Power plants depend on thermodynamics to convert heat into electricity efficiently.
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Q5. Thermodynamics is NOT concerned with:
Explanation: Rate of reaction is a kinetic concern, not a thermodynamic one.
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Q4. Which of the following best represents a thermodynamic system?
Explanation: Steam in a piston-cylinder is a good example of a defined thermodynamic system
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Q3. Thermodynamics is based on:
Explanation: Thermodynamic laws are derived from consistent experimental observations.
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Q2. Which of the following is a primary concern of thermodynamics?
Explanation: Thermodynamics focuses on how energy is converted from one form to another.
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Q1. What does thermodynamics study?
Explanation: Thermodynamics deals with the transformation and transfer of heat and energy.
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