Thermodynamics MCQs Aeronautical Engineering

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The first law of thermodynamics is essentially a statement of the conservation of:

a) Energy
b) Momentum
c) Mass
d) Force
Answer: a) Energy
The second law of thermodynamics introduces the concept of:

a) Entropy
b) Enthalpy
c) Internal energy
d) Heat capacity
Answer: a) Entropy
In a closed system, the change in internal energy is equal to:

a) The heat added to the system minus the work done by the system
b) The work done by the system minus the heat added to the system
c) The heat added to the system plus the work done by the system
d) The change in volume of the system
Answer: a) The heat added to the system minus the work done by the system
The Carnot cycle consists of:

a) Two isothermal processes and two adiabatic processes
b) Two isentropic processes and two isothermal processes
c) Two isobaric processes and two isochoric processes
d) Two adiabatic processes and two isobaric processes
Answer: a) Two isothermal processes and two adiabatic processes
In an isothermal process, the temperature:

a) Remains constant
b) Increases
c) Decreases
d) Varies linearly
Answer: a) Remains constant

The specific heat capacity of a substance is:

a) The amount of heat required to change the temperature of unit mass of the substance by one degree Celsius
b) The heat required to change the phase of the substance
c) The heat required to change the pressure of the substance
d) The amount of heat required to increase the volume of the substance
Answer: a) The amount of heat required to change the temperature of unit mass of the substance by one degree Celsius
The enthalpy of a system is defined as:

a) The internal energy plus the product of pressure and volume
b) The internal energy minus the product of pressure and volume
c) The product of pressure and volume minus the internal energy
d) The product of pressure and volume plus the internal energy
Answer: a) The internal energy plus the product of pressure and volume
A thermodynamic process is called isentropic if:

a) The entropy remains constant
b) The temperature remains constant
c) The pressure remains constant
d) The volume remains constant
Answer: a) The entropy remains constant
The efficiency of a Carnot engine depends on:

a) The temperatures of the hot and cold reservoirs
b) The type of working substance
c) The size of the engine
d) The speed of operation
Answer: a) The temperatures of the hot and cold reservoirs
Thermodynamic Cycles
The Brayton cycle is used in:

a) Gas turbine engines
b) Steam engines
c) Refrigerators
d) Air conditioners
Answer: a) Gas turbine engines
In a Rankine cycle, the working fluid is typically:

a) Water/steam
b) Air
c) Refrigerant
d) Hydrogen
Answer: a) Water/steam
The Otto cycle is used in:

a) Internal combustion engines
b) Jet engines
c) Refrigeration systems
d) Gas turbines
Answer: a) Internal combustion engines
In the refrigeration cycle, the process where the refrigerant absorbs heat is:

a) Evaporation
b) Condensation
c) Compression
d) Expansion
Answer: a) Evaporation
The thermal efficiency of the Rankine cycle increases with:

a) Increasing the temperature of the steam entering the turbine
b) Decreasing the temperature of the condenser
c) Increasing the pressure in the condenser
d) Decreasing the pressure in the boiler
Answer: a) Increasing the temperature of the steam entering the turbine
In the ideal Rankine cycle, the process of vaporization occurs at:

a) Constant pressure
b) Constant volume
c) Constant temperature
d) Constant entropy
Answer: a) Constant pressure
In an ideal Brayton cycle, the work output is:

a) The difference between the heat added and the heat rejected
b) The difference between the work done on the system and the work done by the system
c) The product of the pressure ratio and the temperature difference
d) The heat absorbed by the working fluid
Answer: a) The difference between the heat added and the heat rejected

The term “regenerative cycle” refers to:

a) A cycle where some of the waste heat is recovered and used to preheat the working fluid
b) A cycle where the working fluid is regenerated after each cycle
c) A cycle that uses only renewable energy sources
d) A cycle that operates without any heat rejection
Answer: a) A cycle where some of the waste heat is recovered and used to preheat the working fluid
Properties of Gases and Fluids
The specific volume of a gas is:

a) The volume occupied by a unit mass of the gas
b) The mass of the gas per unit volume
c) The volume occupied by the gas per unit pressure
d) The heat capacity per unit mass
Answer: a) The volume occupied by a unit mass of the gas
The term “enthalpy” is used to describe:

a) The total heat content of a system
b) The heat required to change the temperature of a unit mass
c) The heat required to change the phase of a substance
d) The energy stored in the system
Answer: a) The total heat content of a system
The ideal gas law assumes that:

a) The gas molecules occupy no volume and experience no intermolecular forces
b) The gas molecules have significant volume and experience strong intermolecular forces
c) The gas molecules are inelastic
d) The gas molecules are non-reactive
Answer: a) The gas molecules occupy no volume and experience no intermolecular forces

The heat capacity at constant volume
𝐢𝑣Cv is:

a) The amount of heat required to raise the temperature of a unit mass of the substance by one degree Celsius at constant volume
b) The amount of heat required to raise the temperature of a unit mass of the substance by one degree Celsius at constant pressure
c) The heat required to change the phase of the substance at constant pressure
d) The heat required to change the pressure of the substance at constant volume
Answer: a) The amount of heat required to raise the temperature of a unit mass of the substance by one degree Celsius at constant volume
The Joule-Thomson effect describes:

a) The change in temperature of a gas when it is allowed to expand adiabatically
b) The change in temperature of a gas when it is allowed to expand isothermally
c) The change in temperature of a gas when it is compressed isothermally
d) The change in temperature of a gas when it is allowed to expand at constant enthalpy
Answer: d) The change in temperature of a gas when it is allowed to expand at constant enthalpy
The term “saturated vapor” refers to:

a) The vapor that is in equilibrium with its liquid phase at a given temperature
b) The vapor that has a higher temperature than the liquid phase
c) The vapor that is fully condensed
d) The vapor that has no interaction with the liquid phase
Answer: a) The vapor that is in equilibrium with its liquid phase at a given temperature
The Clausius-Clapeyron equation relates:

a) The change in pressure with temperature for a phase transition
b) The change in volume with temperature for an ideal gas
c) The change in enthalpy with temperature for a chemical reaction
d) The change in entropy with pressure for a chemical reaction
Answer: a) The change in pressure with temperature for a phase transition
In an adiabatic process, heat transfer:

a) Is zero
b) Is constant
c) Increases with temperature
d) Decreases with pressure
Answer: a) Is zero
Combustion and Chemical Thermodynamics
The higher heating value (HHV) of a fuel refers to:

a) The total heat released when the fuel is burned, including the heat of vaporization of water
b) The heat released excluding the heat of vaporization of water
c) The heat required to heat the fuel to its ignition temperature
d) The energy required to initiate combustion
Answer: a) The total heat released when the fuel is burned, including the heat of vaporization of water
The adiabatic flame temperature is:

a) The maximum temperature that can be achieved in a combustion process without heat losses
b) The temperature at which the fuel starts to burn
c) The temperature at which the combustion products are in equilibrium with the reactants
d) The temperature at which the fuel and oxidizer are mixed
Answer: a) The maximum temperature that can be achieved in a combustion process without heat losses
The process of combustion is characterized by:

a) The chemical reaction between a fuel and an oxidizer
b) The absorption of heat without a chemical change
c) The physical mixing of fuel and oxidizer
d) The cooling of a hot gas to room temperature
Answer: a) The chemical reaction between a fuel and an oxidizer
In a chemical reaction, the change in Gibbs free energy
Ξ”
𝐺
Ξ”G determines:

a) The spontaneity of the reaction
b) The rate of the reaction
c) The equilibrium constant of the reaction
d) The activation energy of the reaction
Answer: a) The spontaneity of the reaction
The concept of chemical equilibrium is described by:

a) The equality of the forward and reverse reaction rates
b) The equal concentration of reactants and products
c) The maximum temperature achieved in a reaction
d) The minimum pressure required for the reaction
Answer: a) The equality of the forward and reverse reaction rates
The term “enthalpy of formation” refers to:

a) The heat released or absorbed when one mole of a compound is formed from its elements
b) The heat required to change the phase of a substance
c) The heat required to dissolve a substance in a solvent
d) The heat released during a chemical reaction at constant volume
Answer: a) The heat released or absorbed when one mole of a compound is formed from its elements
The stoichiometric air-fuel ratio is:

a) The ratio of air to fuel required for complete combustion
b) The ratio of air to fuel for partial combustion
c) The ratio of fuel to air in a combustion chamber
d) The ratio of exhaust gases to fuel in an engine
Answer: a) The ratio of air to fuel required for complete combustion
The term “thermal efficiency” of a combustion engine is defined as:

a) The ratio of work output to heat input
b) The ratio of heat rejected to work output
c) The ratio of fuel consumption to power output
d) The ratio of heat absorbed to fuel consumption
Answer: a) The ratio of work output to heat input
In combustion analysis, the term “combustion efficiency” refers to:

a) The percentage of energy in the fuel that is converted to useful work
b) The percentage of fuel that is converted to waste products
c) The percentage of heat that is recovered from the exhaust gases
d) The percentage of air that is used in the combustion process
Answer: a) The percentage of energy in the fuel that is converted to useful work
In an ideal combustion process, the flame temperature is:

a) The highest temperature achievable with complete combustion
b) The temperature at which the fuel ignites
c) The temperature of the combustion products at equilibrium
d) The temperature required for the fuel to vaporize
Answer: a) The highest temperature achievable with complete combustion
Heat Transfer and Thermodynamics
The heat transfer by conduction depends on:

a) The temperature gradient and thermal conductivity of the material
b) The temperature difference between the two bodies
c) The velocity of the fluid
d) The surface area of the material
Answer: a) The temperature gradient and thermal conductivity of the material
The heat transfer coefficient is a measure of:

a) The efficiency of heat transfer between a solid surface and a fluid
b) The rate of heat loss through conduction
c) The thermal resistance of a material
d) The amount of heat absorbed by a material
Answer: a) The efficiency of heat transfer between a solid surface and a fluid
The term “thermal resistance” in heat transfer refers to:

a) The ability of a material to resist heat flow
b) The rate at which heat is transferred through a material
c) The temperature difference required for heat transfer
d) The thermal conductivity of a material
Answer: a) The ability of a material to resist heat flow
In a heat exchanger, the purpose is to:

a) Transfer heat between two or more fluids
b) Increase the temperature of a single fluid
c) Reduce the pressure of a fluid
d) Increase the volume of a fluid
Answer: a) Transfer heat between two or more fluids
The Stefan-Boltzmann law relates to:

a) The heat radiated by a black body to its temperature
b) The heat conducted through a material to its thickness
c) The heat transferred by convection to the fluid velocity
d) The heat absorbed by a material to its specific heat capacity
Answer: a) The heat radiated by a black body to its temperature
The term “latent heat” refers to:

a) The heat required for a phase change at constant temperature
b) The heat required to raise the temperature of a substance
c) The heat lost during combustion
d) The heat absorbed by a fluid during heating
Answer: a) The heat required for a phase change at constant temperature
The process of heat transfer by convection involves:

a) The movement of fluid or gas
b) The emission of electromagnetic waves
c) The direct contact between materials
d) The diffusion of heat through a solid
Answer: a) The movement of fluid or gas
The effectiveness of a heat exchanger is defined as:

a) The ratio of actual heat transfer to the maximum possible heat transfer
b) The ratio of the heat capacity of the fluids
c) The ratio of the temperature difference to the heat capacity
d) The ratio of heat lost to the heat gained
Answer: a) The ratio of actual heat transfer to the maximum possible heat transfer
The concept of “enthalpy” is used to describe:

a) The total heat content of a system
b) The change in temperature of a system
c) The rate of heat transfer through a material
d) The amount of work done by a system
Answer: a) The total heat content of a system
The first law of thermodynamics states:

a) Energy cannot be created or destroyed, only transformed
b) Entropy of an isolated system always increases
c) Heat transfer is always from hot to cold bodies
d) The pressure of a gas is directly proportional to its volume
Answer: a) Energy cannot be created or destroyed, only transformed

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