 # Quiz:Mechanical Engineering 23 April 2020

Quiz: Mechanical Engineering
Exam: UPPSC AE
Topic: Thermal Engineering

Each question carries 3 mark.
Negative marking: 1 mark
Time: 10 Minute

Q1. Which one of the following are intensive properties?
1. Kinetic energy
2. Specific entropy
3. Pressure
4. Enthalpy
Codes:
(a) 1 and 3
(b) 2 and 3
(c) 1,3 and 4
(d) 2 and 4

Q2. It is desired to bring about a change in the state of a system by performing work on the system under adiabatic conditions.
(a) The amount of work needed is path dependent
(b) Work alone cannot bring about such a change of state
(c) The amount of work needed is independent of path
(d) More information is needed to conclude anything about the path dependence or otherwise of the work needed

Q3. ‘’Heat cannot be transported from a system at low temperature to another system at high temperature without the aid of external agency’’. This statement of second law is attributed to
(a) Clausius
(b) Joule Thomson
(c) Max Planck
(d) Gay-Lussac

Q4. In statistical thermodynamics, entropy is defined as
1.measure of irreversibility of a system
2.a universal property
3.degree of randomness
4.thermodynamic probability of disorderness
Which of the above is/are correct?
(a) 1 and 3
(b) 1, 2 and 3
(c) 2, 3 and 4
(d) 1, 3 and 4

Q5. Availability of a system at any given state is
(a) a property of a system
(b) the total energy of the system
(c) the maximum work obtainable as system goes to dead state
(d) the maximum useful work obtainable as the system goes to dead state

Q6. Change of state e.g. freezing, melting, evaporation and condensation is an
(b) Isopiestic process
(c) Isothermal process
(d) Isochoric process

Q7. For an ideal gas the value of Joule-Thomson coefficient is
(a) zero
(b) 0.5
(c) unity
(d) infinite

Q8. When a gas is to be stored, the type of compression that would be ideal is
(a) Isothermal
(c) Polytropic
(d) Constant volume

Q9. Gibb’s free energy (G) is given by
(a) G=H-TS
(b) G=H/TS
(c) G=U-TS
(d) None of these

Q10. Thermo-electric refrigeration is based on
(a) Peltier effect
(b) Joule effect
(c) Joule-Thomson throttling

Solutions

S1. Ans.(b)
Sol. Intensive properties are those properties which do not depend on mass e.g. pressure, temperature, all specific properties etc.

S2. Ans.(a)
Sol.

S3. Ans.(a)
Sol. According to Clausius statement of second law of thermodynamics, ‘’ heat cannot be transferred from a lower temperature to higher temperature without the aid of external agency.’’

S4. Ans.(d)
Sol. Entropy is a measure of irreversibility in the system, it is a degree of randomness and probability of disorderness in the system.

S5. Ans.(d)
Sol. Availability of a system at any given state is the maximum useful work obtainable as the system goes to dead state.

S6. Ans.(b)
Sol. Freezing, melting, evaporation and condensation all are phase changing process. All the phase change take place at constant pressure process.

S7. Ans.(a)
Sol. Joule-Thomson coefficient (μ) for an ideal gas =0

S8. Ans.(a)
Sol. Isothermal compression is an ideal process for compressed air storage because this process consumes the least work.

S9. Ans.(a)
Sol. Gibb’s free energy function is given by G=H-TS

S10. Ans.(a)
Sol. Thermo-electric refrigeration works on the principle of Peltier effect.