# 439 Thermodynamic MCQ For All Mechanical Exams

76)Integral of dQ/T is independent of reversible path connecting between two points.

1. a) true
2. b) false

Ans-A

77)Integral of dQ/T of a reversible path is given by

1. a) Si-Sf
2. b) Sf-Si
3. c) Si+Sf
4. d) -Si-Sf

Ans-B

78)Entropy is a

1. a) path function, intensive property
2. b) path function, extensive property
3. c) point function, intensive property
4. d) point function, extensive property

Ans-D

79)Specific entropy is given by( where m is the mass)

1. a) Sm
2. b) m/S
3. c) S/m
4. d) none of the mentioned

Ans-C

80)For any process which is undergone by a system

1. a) dQ/T>=ds
2. b) dQ/T<=ds
3. c) dQ/T≠ds
4. d) none of the mentioned

Ans-B

81)For a reversible process,

1. a) dS=dQ/T
2. b) dS>dQ/T
3. c) dS<dQ/T
4. d) none of the mentioned

Ans-A

82)For an irreversible process,

1. a) dS=dQ/T
2. b) dS>dQ/T
3. c) dS<dQ/T
4. d) none of the mentioned

Ans-B

83)For two different paths between same two points, entropy change is

1. a) depends on path taken
2. b) different
3. c) same
4. d) none of the mentioned

Ans-C

84)For the general case, we can write

1. a) S2-S1<=dQ/T for a path
2. b) S2-S1>=dQ/T for a path
3. c) S2-S1≠dQ/T for a path
4. d) none of the mentioned

Ans-B

85)When two equilibrium states are infinitesimally near,

1. a) dQ/T=dS
2. b) dQ/T>dS
3. c) dQ/T<dS
4. d) none of the mentioned

Ans-A

86)For a reversible heat transfer and process being adiabatic, which of the following is true?

1. a) dQ=0
2. b) dS=0
3. c) S=constant
4. d) all of the mentioned

Ans-D

87)A reversible adiabatic process is an isentropic process.

1. a) true
2. b) false

Ans-A

88)The area under the curve ∫TdS is equal to the

1. a) work done
2. b) heat transferred
3. c) internal energy change
4. d) none of the mentioned

Ans-B

89)Net work in a Carnot cycle is given by (T1=temperature of heat addition and T2=temperature of heat rejection)

1. a) (T2-T1)(S1-S4)
2. b) (T1-T2)(S1-S4)
3. c) (T1-T2)(S4-S1)
4. d) none of the mentioned

Ans-B

4. d) none of the mentioned

Ans-C

4. d) none of the mentioned

Ans-A

92)The entropy of an isolated system can never ____

1. a) increase
2. b) decrease
3. c) be zero
4. d) none of the mentioned

Ans-B

93)Entropy may decrease locally at some region within the isolated system. How can this statement be justified?

1. a) this cannot be possible
2. b) this is possible because entropy of an isolated system can decrease.
3. c) it must be compensated by a greater increase of entropy somewhere within the system.
4. d) none of the mentioned

Ans-C

94)Clausius summarized the first and second laws of thermodynamics as

1. a) the energy of the world is constant
2. b) the entropy of the world tends towards a maximum
3. c) both of the mentioned
4. d) none of the mentioned

Ans-C

95)The entropy of an isolated system always ____ and becomes a ____ at the state of equilibrium.

1. a) decreases, minimum
2. b) increases, maximum
3. c) increases, minimum
4. d) decreases, maximum

Ans-B

96)The final temperatures of two bodies, initially at T1 and T2 can range from

1. a) (T1-T2)/2 to sqrt(T1*T2)
2. b) (T1+T2)/2 to sqrt(T1*T2)
3. c) (T1+T2)/2 to (T1*T2)
4. d) (T1-T2)/2 to (T1*T2)

Ans-B

97)Which of the following processes exhibit external mechanical irreversibility?

1. a) isothermal dissipation of work
2. b) adiabatic dissipation of work
3. c) both of the mentioned
4. d) none of the mentioned

Ans-C

98)Entropy transfer for an adiabatic transfer is zero.

1. a) true
2. b) false

Ans-A

99)If heat Q flows reversibly from the system to the surroundings at To,

1. a) entropy increase of the surroundings is Q/To
2. b) entropy of the system is reduced by Q/To
3. c) system has lost entropy to the surroundings
4. d) all of the mentioned

Ans-D

100)____ is exchanged during work interaction, whereas both ____ and ____ are exchanged during heat transfer.

1. a) energy, energy and entropy
2. b) entropy, energy and entropy
3. c) mass, energy and entropy
4. d) none of the mentioned

Ans-A

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