# Thermodynamics Questions and Answers – Temperature-Entropy Plot

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This set of Thermodynamics Multiple Choice Questions & Answers (MCQs) focuses on “Temperature-Entropy Plot”.

1. For a reversible heat transfer and process being adiabatic, which of the following is true?
a) dQ=0
b) dS=0
c) S=constant
d) all of the mentioned

Explanation: dQ=0 since process is reversible and adiabatic and dS=dQ/T.

2. A reversible adiabatic process is an isentropic process.
a) true
b) false

Explanation: dQ=0 and dS=0 and hence S=constant.

3. The area under the curve ∫TdS is equal to the
a) work done
b) heat transferred
c) internal energy change
d) none of the mentioned

Explanation: Q(reversible)=∫TdS.

4. Which of the following statement is true?
a) for reversible isothermal heat transfer, Q=t(Sf-Si)
b) for reversible adiabatic process, S=constant
c) both of the mentioned
d) none of the mentioned

Explanation: For reversible isothermal heat transfer, T=constant and for reversible adiabatic process, dS=0.

5. A Carnot cycle has following processes.
a) 4 reversible isotherms
c) 2 reversible isotherms and 2 reversible adiabatics
d) none of the mentioned

Explanation: Two reversible isotherms and two reversible adiabatics constitute a Carnot cycle.

6. Net work in a Carnot cycle is given by (T1=temperature of heat addition and T2=temperature of heat rejection)
a) (T2-T1)(S1-S4)
b) (T1-T2)(S1-S4)
c) (T1-T2)(S4-S1)
d) none of the mentioned

Explanation: Net work=Q1-Q2=(T1-T2)(S1-S4).

7. According to the principle of Caratheodory, the first law in differential form is written as dQ=Adx+Bdy+Cdz.
a) true
b) false

Explanation: Here, x,y,z are the three thermodynamic coordinates and A,B,C are the functions of x,y,z.

d) none of the mentioned

d) none of the mentioned

Explanation: This comes from Caratheodory’s theorem.

10. The infinitesimal change in entropy dS due to reversible heat transfer dQ at temperature T is dS=dQ/T.
a) true
b) false 