Thermodynamics

61. If a system after undergoing a series of processes, returns to the initial state then

  1. process is thermodynamically in equilibrium
  2. process is executed in closed system cycle
  3. its entropy will change due to irreversibility
  4. sum of heat and work transfer will be zero
  5. no work will be done by the system.

Correct answer: (D)
sum of heat and work transfer will be zero

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

  1. more
  2. less
  3. equal
  4. depends on other factors
  5. none of the above.

Correct answer: (C)
equal

63. If heat be exchanged in a reversible manner, which of the following property of the working substance will change accordingly

  1. temperature
  2. enthalpy
  3. internal energy
  4. entropy
  5. all of the above.

Correct answer: (D)
entropy

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

  1. volume
  2. pressure
  3. temperature
  4. enthalpy
  5. entropy.

Correct answer: (A)
volume

65. In a Carnot cycle, heat is transferred at

  1. constant pressure
  2. constant volume
  3. constant temperature
  4. constant enthaply
  5. any one of the above.

Correct answer: (C)
constant temperature

66. In a free expansion process

  1. work done is zero
  2. heat transfer is zero
  3. both (a) and (b) above
  4. work done is zero but heat increases
  5. work done is zero but heat decreases.

Correct answer: (C)
both (a) and (b) above

67. In a non-flow reversible process for which p = (- 3V+ 15) x 105N/m2,V changes from 1 m to 2 m3. The work done will be about

  1. 100 xlOO5 joules
  2. lxlO5 joules
  3. 10 xlO5 joules
  4. 10 xlO5 kilo joules
  5. 10xl04ki\ojoules.

Correct answer: (C)
10 xlO5 joules

68. In an isothermal process, the internal energy

  1. increases
  2. decreases
  3. remains constant
  4. first increases and then decreases
  5. first decreases and then increases.

Correct answer: (C)
remains constant

69. In an isothermal process, the internal energy of gas molecules

  1. increases
  2. decreases
  3. remains constant
  4. may increase/decrease depending on the properties of gas
  5. shows unpredictable behaviour.

Correct answer: (C)
remains constant

70. In order that a cycle be reversible, following must be satisfied

  1. free expansion or friction resisted expansion/compression process should not be encountered
  2. when heat is being absorbed, temperature of hot source and working sub¬stance should be same
  3. when beat is being rejected, temperature of cold source and working sub-stance should be same
  4. all of the above
  5. none of the above.

Correct answer: (D)
all of the above

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