Mechanical Engineering Thermodynamics – Set 12

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Q1. For which of the following substances, the internal energy and enthalpy are the functions of temperature only

(A) Any gas
(B) Saturated steam
(C) Water
(D) Perfect gas

Answer: (D) Perfect gas

Q2. The compression ratio for Diesel engines is

(A) 15 to 20
(B) 5 to 8
(C) 3 to 6
(D) 20 to 30

Answer: (A) 15 to 20

Q3. If both Stirling and Carnot cycles operate within the same temperature limits, then efficiency of Stirling cycle as compared to Carnot cycle

(A) More
(B) Less
(C) Equal
(D) Depends on other factors

Answer: (C) Equal

Q4. The following cycle is used for air craft refrigeration

(A) Brayton cycle
(B) Joule cycle
(C) Carnot cycle
(D) Reversed Brayton cycle

Answer: (D) Reversed Brayton cycle

Q5. A cycle consisting of __ and two isothermal processes is known as Stirling cycle.

(A) Two constant pressure
(B) Two constant volume
(C) Two isentropic
(D) One constant pressure, one constant volume

Answer: (B) Two constant volume

Q6. Otto cycle is also known as

(A) Constant pressure cycle
(B) Constant volume cycle
(C) Constant temperature cycle
(D) Constant temperature and pressure cycle

Answer: (B) Constant volume cycle

Q7. When the expansion or compression takes place according to the law pvn = C, the process is known as

(A) Isothermal process
(B) Adiabatic process
(C) Hyperbolic process
(D) Polytropic process

Answer: (D) Polytropic process

Q8. Energy can neither be created nor destroyed, but it can be transformed from one form to another. This statement is known as

(A) Zeroth law of thermodynamics
(B) First law of thermodynamics
(C) Second law of thermodynamics
(D) Kinetic theory of gases

Answer: (B) First law of thermodynamics

Q9. In a reversible adiabatic process, the ratio of T1/T2 is equal to

(A) (p2/p1)γ – 1/ γ
(B) (p1/p2)γ – 1/ γ
(C) (v2/v1)γ – 1/ γ
(D) (v1/v2)γ – 1/ γ

Answer: (B) (p1/p2)γ – 1/ γ

Q10. The efficiency of Stirling cycle is __ Carnot cycle.

(A) Greater than
(B) Less than
(C) Equal to
(D) None of these

Answer: (C) Equal to

Q11. Mond gas is obtained by

(A) Partial combustion of coal, coke, anthracite coal or charcoal in a mixed air steam blast
(B) Carbonization of bituminous coal
(C) Passing steam over incandescent coke
(D) Passing air and a large amount of steam over waste coal at about 650°C

Answer: (D) Passing air and a large amount of steam over waste coal at about 650°C

Q12. Relation between cp and cv is given by (where cp = Specific heat at constant pressure, cv = Specific heat at constant volume, γ = cp/cv, known as adiabatic index, and R = Gas constant)

(A) cv/ cp =R
(B) cp – cv = R
(C) cv = R/ γ-1
(D) Both (B) and (C)

Answer: (D) Both (B) and (C)

Q13. According to Regnault’s law, the specific heat at constant pressure (cp) and specific heat at constant volume (cv) _ with the change in pressure and temperature of the gas.

(A) Change
(B) Do not change
(C) Both (A) and (B)
(D) None of these

Answer: (B) Do not change

Q14. Those substances which have so far not been resolved by any means into other substances of simpler form are called

(A) Elements
(B) Compounds
(C) Atoms
(D) Molecules

Answer:(A) Elements

Q15. When a system changes its state from one equilibrium state to another equilibrium state, then the path of successive states through which the system has passed, is known as

(A) Thermodynamic law
(B) Thermodynamic process
(C) Thermodynamic cycle
(D) None of these

Answer: (B) Thermodynamic process

Q16. The general law for the expansion or compression of gases, is

(A) pv = C
(B) pv = m R T
(C) pvn = C
(D) pvγ = C

Answer: (C) pvn = C

Q17. Work-done in a free expansion process is

(A) Zero
(B) Minimum
(C) Maximum
(D) Positive

Answer: (A) Zero

Q18. One kg of carbon requires 4/3 kg of oxygen and produces __ kg of carbon monoxide gas.

(A) 8/3
(B) 11/3
(C) 11/7
(D) 7/3

Answer: (D) 7/3

Q19. All perfect gases change in volume by 1/273th of its original volume at 0°C for every 1°C change in temperature, when the pressure remains constant. This statement is called

(A) Boyle’s law
(B) Charles’ law
(C) Gay-Lussac law
(D) Joule’s law

Answer:(B) Charles’ law

Q20. The condition for the reversibility of a cycle is

(A) The pressure and temperature of the working substance must not differ, appreciably, from those of the surroundings at any stage in the process
(B) All the processes, taking place in the cycle of operation, must be extremely slow
(C) The working parts of the engine must be friction free
(D) All of the above

Answer: (D) All of the above

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