Engineering Thermodynamics Set 13

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This set of Engineering Thermodynamics Multiple Choice Questions & Answers (MCQs) focuses on Engineering Thermodynamics Set 13

Q1 | Example of reversed heat engine is
  • heat pump
  • refrigerator
  • both of the mentioned
  • none of the mentioned
Q2 | Efficiency of a reversible heat engine is given by
  • 1-(t1/t2)
  • 1-(t2/t1)
  • (t1/t2)-1
  • (t2/t1)-1
Q3 | For a reversible refrigerator, Coefficient of Performance is given by
  • t2/(t1-t2)
  • t1/(t1-t2)
  • t2/(t2-t1)
  • t1/(t2-t1)
Q4 | Entropy principle is the quantitative statement of the second law of thermodynamics.
  • true
  • false
Q5 | Which of the following can be considered as an application of entropy principle?
  • transfer of heat through a finite temperature difference
  • mixing of two fluids
  • maximum temperature obtainable from two finite bodies
  • all of the mentioned
Q6 | The final temperatures of two bodies, initially at T1 and T2 can range from
  • (t1-t2)/2 to sqrt(t1*t2)
  • (t1+t2)/2 to sqrt(t1*t2)
  • (t1+t2)/2 to (t1*t2) d) (t1-t2)/2 to (t1*t2)
Q7 | Which of the following processes exhibit external mechanical irreversibility?
  • isothermal dissipation of work
  • adiabatic dissipation of work
  • both of the mentioned
  • none of the mentioned
Q8 | Which of the following is an example of low grade energy?
  • heat or thermal energy
  • heat from nuclear fission or fusion
  • heat from combustion of fossil fuel
  • all of the mentioned
Q9 | Which of the following is an example of high grade energy?
  • mechanical work
  • electrical energy
  • water power and wind power
  • all of the mentioned
Q10 | The unavailable energy is the product of the lowest temperature of heat rejection and the change of entropy of system during the process of supplying heat.
  • true
  • false
Q11 | The lowest practicable temperature of heat rejected is the
  • given temperature
  • 0k
  • temperature of surroundings
  • 273k
Q12 | Exergy is lost due to
  • irreversible heat transfer
  • through finite temperature difference
  • during the process of heat addition
  • all of the mentioned
Q13 | Which of the following is a type of energy?
  • high grade energy
  • low grade energy
  • both of the mentioned
  • none of the mentioned
Q14 | The complete conversion of heat into shaft- work is impossible.
  • true
  • false
Q15 | Energy is said to be degraded each time it flows through a finite temperature difference.
  • true
  • false
Q16 | When considering a finite energy source, its working fluid expands,
  • reversibly
  • adiabatically
  • reversibly and adiabatically
  • none of the mentioned
Q17 | The entropy of any closed system can increase in which if the following way?
  • by heat interaction in which there is entropy transfer
  • dissipative effects or internal irreversibilities
  • both of the mentioned
  • none of the mentioned
Q18 | The entropy increase due to internal irreversibility is also called entropy production or entropy generation.
  • true
  • false
Q19 | Which of the following statement is true?
  • if the isentropic process is reversible, it must be adiabatic
  • if the isentropic process is adiabatic, it cannot but be reversible
  • if the process is adiabatic and reversible, it must be isentropic
  • all of the mentioned
Q20 | Lost work is given by
  • pdv-dw
  • pdv+dw
  • -pdv-dw
  • pdv*dw
Q21 | Which of the following statement is false?
  • for a reversible process, entropy generation is zero
  • the entropy generation does not depend on the path the system follows
  • for an irreversible process, entropy generation is greater than zero
  • none of the mentioned
Q22 | Mass and energy are conserved quantities, but entropy is generally not conserved.
  • true
  • false
Q23 | A chip dissipates 2 kJ of electric work and rejects it as heat transfer from its surface which is at 50°C to 25°C air. How much entropy is generated outside the chip?
  • 0.419 j/k
  • 0.519 j/k
  • 0.619 j/k
  • 0.719 j/k
Q24 | Entropy increase dS of the system can be expressed as
  • ds=ds(due to external heat interaction)- ds(due to internal irreversibility)
  • ds=ds(due to external heat interaction)+ds(due to internal irreversibility)
  • ds=-ds(due to external heat interaction)- ds(due to internal irreversibility)
  • ds=-ds(due to external heat interaction)+ds(due to internal irreversibility)
Q25 | If the path A causes more entropy generation than path B, then
  • path a is more irreversible than path b
  • path a involves more lost work
  • both of the mentioned
  • none of the mentioned