Mechanical Engineering Thermodynamics – Set 10

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Q1. The hard coke is obtained when carbonization of coal is carried out at

(A) 500° to 700°C
(B) 700° to 900°C
(C) 300° to 500°C
(D) 900° to 1100°C

Answer: (D) 900° to 1100°C


Q2. The ratio of two specific heats of air is equal to

(A) 0.17
(B) 0.24
(C) 0.1
(D) 1.41

Answer: (D) 1.41


Q3. The fuel mostly used in steam boilers is

(A) Brown coal
(B) Peat
(C) Coking bituminous coal
(D) Non-coking bituminous coal

Answer:(D) Non-coking bituminous coal


Q4. A perfect gas at 27°C is heated at constant pressure till its volume is double. The final temperature is

(A) 54°C
(B) 327°C
(C) 108°C
(D) 654°C

Answer: (B) 327°C


Q5. One kg of carbon requires 4/3 kg of oxygen and produces __ kg of carbon monoxide gas.

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

Answer: (B) 7/3


Q6. Minimum work in compressor is possible when the value of adiabatic index ‘n’ is equal to

(A) 0.75
(B) 1
(C) 1.27
(D) 1.35

Answer: (B) 1


Q7. Total heat of a substance is also known as

(A) Internal energy
(B) Entropy
(C) Thermal capacity
(D) Enthalpy

Answer: (D) Enthalpy


Q8. Producer gas is obtained by

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

Answer: (B) Partial combustion of coal, coke, anthracite coal or charcoal in a mixed air steam blast


Q9. A perpetual motion machine is

(A) A thermodynamic machine
(B) A non-thermodynamic machine
(C) A hypothetical machine
(D) A hypothetical machine whose operation would violate the laws of thermodynamics

Answer: (D) A hypothetical machine whose operation would violate the laws of thermodynamics


Q10. Which law states that the specific heat of a gas remains constant at all temperatures and pressures?

(A) Charles’ Law
(B) Joule’s Law
(C) Regnault’s Law
(D) Boyle’s Law

Answer: (C) Regnault’s Law


Q11. During which of the following process does heat rejection takes place in Carnot cycle?

(A) Isothermal expansion
(B) Isentropic expansion
(C) Isothermal compression
(D) Isentropic compression

Answer: (C) Isothermal compression


Q12. During throttling process

(A) Heat exchange does not take place
(B) No work is done by expanding steam
(C) There is no change of internal energy of steam
(D) All of the above

Answer: (C) Isothermal compression

Q13. The amount of heat required to raise the temperature of the unit mass of gas through one degree at constant volume, is called

(A) Specific heat at constant volume
(B) Specific heat at constant pressure
(C) Kilo Joule
(D) None of these

Answer: (A) Specific heat at constant volume


Q14. The ideal efficiency of a Brayton cycle without regeneration, with increase in pressure ratio will

(A) Increase
(B) Decrease
(C) Remain unchanged
(D) Increase/decrease depending on application

Answer: (A) Increase


Q15. The main cause for the irreversibility is

(A) Unrestricted expansion
(B) Mechanical and fluid friction
(C) Heat transfer with a finite temperature difference
(D) All of the above

Answer: (D) All of the above


Q16. Which of the following is an intensive property of a thermodynamic system?

(A) Mass
(B) Temperature
(C) Energy
(D) Volume

Answer: (B) Temperature


Q17. Boyle’s law i.e. pV = constant is applicable to gases under

(A) All ranges of pressures
(B) Only small range of pressures
(C) High range of pressures
(D) Steady change of pressures

Answer: (B) Only small range of pressures


Q18. An isolated system is one in which

(A) Mass does not cross boundaries of the system, though energy may do so
(B) Neither mass nor energy crosses the boundaries of the system
(C) Both energy and mass cross the boundaries of the system
(D) Mass crosses the boundary but not the energy

Answer: (B) Neither mass nor energy crosses the boundaries of the system


Q19. If value of n is infinitely large in a polytropic process pVn = C, then the process is known as constant

(A) Volume
(B) Pressure
(C) Temperature
(D) Enthalpy

Answer: (A) Volume


Q20. The value of the product of molecular weight and the gas characteristic constant for all the gases in M.K.S. unit is

(A) 29.27 kgfm/mol °K
(B) 8314 kgfm/mol °K
(C) 848 kgfm/mol °K
(D) 427 kgfm/mol °K

Answer: (C) 848 kgfm/mol °K


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