250+ TOP MCQs on Carnot Theorem, Carnot Cycle and Reversed Heat Engine and Answers

Thermodynamics Multiple Choice Questions on “Carnot Theorem, Carnot Cycle and Reversed Heat Engine”.

1. Carnot cycle is a reversible cycle.
a) true
b) false
Answer: a
Clarification: A reversible cycle is an ideal hypothetical cycle in which all processes are reversible.

2. A reversible cycle has following processes.
a) 4 isothermal processes
b) 4 adiabatic processes
c) 2 isothermal and 2 adiabatic processes
d) none of the mentioned
Answer: c
Clarification: Two reversible isotherms and two reversible adiabatics constitute a Carnot cycle.

3. The correct sequence of the processes taking place in a carnot cycle is
a) adiabatic -> adiabatic -> isothermal -> isothermal
b) adiabatic -> isothermal -> adiabatic -> isothermal
c) isothermal -> isothermal -> adiabatic -> adiabatic
d) isothermal -> adiabatic -> isothermal -> adiabatic
Answer: d
Clarification: Carnot cycle consists if these four processes in succession.

4. The reversed heat engine takes heat from a ___ temperature body, then discharges it to a ___ temperature body and ___ an inward flow of network.
a) high, low, receives
b) low, high, receives
c) high, low, gives
d) low, high, gives
Answer: b
Clarification: In reversed heat engine, the magnitude of energy transfers remains same and only directions change.

5. Example of reversed heat engine is
a) heat pump
b) refrigerator
c) both of the mentioned
d) none of the mentioned
Answer: c
Clarification: Heat pump and refrigerator are the types of reversed heat engine.

6. According to Carnot’s theorem, all heat engines operating between a given constant temperature source and sink, none has a higher efficiency than a reversible engine.
a) true
b) false
Answer: a
Clarification: This is the statement of Carnot’s theorem .

7. The efficiency of all reversible heat engines operating between the same heat reservoirs is
a) same
b) independent of the nature of working substance
c) independent of the amount of working substance
d) all of the mentioned
Answer: d
Clarification: This statement is a corollary of Carnot’s theorem.

8. Efficiency of a reversible heat engine is given by
a) 1-(T1/T2)
b) 1-(T2/T1)
c) (T1/T2)-1
d) (T2/T1)-1
Answer: b
Clarification: Efficiency=1-(Q2/Q1) and T2,T1 are temperatures at which heat is rejected and received.

9. For a reversible refrigerator, Coefficient of Performance is given by
a) T2/(T1-T2)
b) T1/(T1-T2)
c) T2/(T2-T1)
d) T1/(T2-T1)
Answer: a
Clarification: For a reversible refrigerator, (Q1/Q2)=(T1/T2).

10. For a reversible heat pump, COP is given by
a) T2/(T1-T2)
b) T1/(T1-T2)
c) T2/(T2-T1)
d) T1/(T2-T1)
Answer: b
Clarification: For a reversible heat pump we have, (Q1/Q2)=(T1/T2).