# Thermodynamics 1

Mechanical Engineering MCQ Question Papers: DRDO, ISRO, Interview

Subject:  Thermodynamics 1

Part 1: List for questions and answers of Thermodynamics

Q1. The characteristic equation of gases pv = mrt holds good for
a) Mono atomic gases
b) Diatomic gas
c) Real gases
d) Ideal gases

Q2. A gas which obeys kinetic theory perfectly is known as
a) Mono atomic gas
b) Diatomic gas
c) Real gas
d) Perfect gas

Q3. Second law of thermodynamics defines
a) Heat
b) Work
c) Enthalpy
d) Entropy

Q4. For a reversible adiabatic process, the change in entropy is
a) Zero
b) Minimum
c) Maximum
d) Infinite

Q5. For any reversible process, the change in entropy of the system and surroundings is
a) Zero
b) Unity
c) Negative
d) Positive

Q6. For any irreversible process the net entropy change is
a) Zero
b) Positive
c) Negative
d) Infinite

Q7. The processes of a Carnot cycle are
a) Two adiabatic and two constant volume
b) One constant volume and one constant pressure and two isentropics
c) Two adiabatics and two isothermals
d) Two isothermals and two isentropics

Q8. Isentropic flow is
b) Ideal fluid flow
c) Perfect gas flow

Q9. In a Carnot engine, when the working substance gives heat to the sink
a) The temperature of the sink increases
b) The temperature of the sink remains the same
c) The temperature of the source decreases
d) The temperatures of both the sink and the source decrease

Q10. If the temperature of the source is increased, the efficiency of the Carnot engine
a) Decreases
b) Increases
c) Does not change
d) Will be equal to the efficiency of a practical engine

Q11. The efficiency of an ideal Carnot engine depends on
a) Working substance
b) On the temperature of the source only
c) On the temperature of the sink only
d) On the temperatures of both the source and the sink

Q12. In a reversible cycle, the entropy of the system
a) Increases
b) Decreases
c) Does not change
d) First increases and then decreases

Q13. A frictionless heat engine can be 100% efficient only if its exhaust temperature is
a) Equal to its input temperature
b) Less than its input temperature
c) 0°C
d) 0°K

Q14. Kelvin-Planck’s law deals with
a) Conservation of energy
b) Conservation of heat
c) Conservation of mass
d) Conversion of heat into work

Q15. The relation, where ‘S’ represents entropy, Q represents heat and T represents temperature (absolute) holds good in which one of the following processes ?
a) Reversible processes only
b) Irreversible processes only
c) Both reversible and irreversible processes
d) All real processes

Q16. The unit of entropy is
a) Kj/kg K
b) Kj/K
c) N/K
d) N-m/kg sec

Q17. A heat source at 800 K losses 2000 kj of heat to a sink (1) at 500 K (2) at 750 K. Determine which heat transfer process is more irreversible?
a) Case (1)
b) Case (2)
c) Either case (1) or case (2)
d) None of the above

Q18. Calculate the entropy transfer in raising a weight by a rotating shaft or flywheel, assuming frictionless motion
a) 0
b) 1
c) Data is insufficient
d) None of the above

Q19. 1600 k.I of energy is transferred iron a heat reservoir at 800 K to another heat reservoir at 400 K. The amount of entropy generated during the process would be
a) 6kj/K
b) 4kj/K
c) 2kj/K
d) Zero

Q20. From a heat reservoir at 500K, an amount of heat equal to 1000 kj is supplied to the engine. The entropy change of heat reservoir will be
a) 2
b) – 2
c) 0.5
d) -0.5

Part 1: List for questions and answers of Thermodynamics