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This set of Engineering Thermodynamics Multiple Choice Questions & Answers (MCQs) focuses on Engineering Thermodynamics Set 3
Q1 | The main cause of the irreversibility is
- a) mechanical & fluid friction
- b) unrestricted expansion
- c) heat transfer with a finite temperature difference
- d) all of the above
Q2 | An isentropic process is always
- a) irreversible & adiabatic
- b) reversible & isothermal
- c) frictionless & irreversible
- d) reversible & adiabatic
Q3 | In the polytropic process equation pvⁿ = constant, if n is infinitely large, theprocess is termed as
- a) constant volume
- b) constant pressure
- c) constant temperature
- d) adiabatic
Q4 | Second law of thermodynamics defines
- a) heat
- b) work
- c) enthalpy
- d) entropy
Q5 | For a reversible adiabatic process, thechange in entropy is
- a) zero
- b) minimum
- c) maximum
- d) infinite
Q6 | For any reversible process, the change in entropy of the system & surroundings is
- a) zero
- b) unity
- c) negative
- d) positive
Q7 | For any irreversible process the netentropy change is
- a) zero
- b) positive
- c) negative
- d) infinite
Q8 | The processes of a Carnot cycle are
- a) two adiabatic & two constant volume
- b) one constant volume &one constant pressure & two isentropies
- c) two adiabatics & two isothermals
- d) two isothermals & two isentropies
Q9 | Isentropic flow is
- a) irreversible adiabatic flow
- b) ideal fluid flow
- c) reversible adiabatic flow
- d) frictionless reversible flo
Q10 | In a carnot engine, when the working substance gives heat to the sink
- a) the temperature of the sink increases
- b) the temperature of the sink remains the same
- c) the temperature of the source decreses
- d) the temperature of the source decrease
Q11 | If the temperature of the source is increased, the efficiency of the Carnotengine
- a) decrease
- b) increase
- c) does not change
- d) will be equal to the efficiency of a practicalengine
Q12 | The efficiency of an ideal Carnot engine depends on
- a) working substance
- b) on the temperature of the source only
- c) on the temperature of the sink only
- d) on the temperatures of both the source & the sink
Q13 | In a reversible cycle, the entropy of thesystem
- a) increases
- b) decreases
- c) does not change
- d) first increases & thendecreases
Q14 | Kelvin-Plank's law deals with
- a) conservation of energy
- b) conservation of heat
- c) conservation of mass
- d) conversion of heat intowork
Q15 | Which of the following statements is correct according to Clausius statement of second law of thermodynamics?
- a) it is impossible to transfer heat from a body at a lower temperature to a body at a higher temperature
- b) it is impossible to transfer heat from a body at a lower temperature to a body at a higher temperature, without the aid of an external source
- c) it is possible to transfer heat from a body at a lower temperature to a body at a higher temperature by using refrigeration cycle
- d) none of the above
Q16 | The property of a working substance which increases or decreases as the heat is supplied or removed in a reversiblemanner is known as
- a) enthalpy
- b) internal energy
- c) entropy
- d) external energy
Q17 | The entropy may be expressed as afunction of
- a) pressure & temperature
- b) temperature & volume
- c) heat & work
- d) all of the above
Q18 | The change of entropy when heat isabsorbed by the gas is
- a) positive
- b) negative
- c) positive or negative
- d) all of the above
Q19 | Which of the following statements is correct?
- a) the increase in entropy is obtained from a given quantity of heat at a low temperature
- b) the change in entropy may be regarded as a measure of the rate of the availability of heat fortransformation into work
- c) the entropy represents the maximum amount of work obtainable per degree drop in temperature
- d) all of the above
Q20 | In an irreversible process, there is a
- a) loss of heat
- b) no loss of work
- c) gain of heat
- d) no gain of heat
Q21 | The efficiency of the Carnot cycle may beincreased by
- a) increasing the highesttemperature
- b) decreasing the highesttemperature
- c) increasing the lowesttemperature
- d) decreasing the lowesttemperature
Q22 | Which of the following is the correct statement?
- a) all the reversible engines have the same efficiency
- b) all the reversible & irreversible engines have the same efficiency
- c) irreversible engines have maximum efficiency
- d) all engines are designed as reversible in order to obtain maximum efficiency
Q23 | The reversible engines are
- a) least efficient
- b) most efficient
- c) having same efficiency asirreversible engines
- d) none of the above
Q24 | Gases could have an infinite number ofspecific heats but only ……. Specific heats are defined
- a) one
- b) two
- c) three
- d) four
Q25 | The area under the T-s (temperature - entropy) curve of any thermodynamicprocess represents
- a) heat rejected only
- b) heat absorbed only
- c) work done during the process
- d) heat absorbed or rejected