Previous Year Thermodynamics Objective Questions Answers

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16. For steady flow through an insulated horizontal constant diameter pipe, this property remains constant-

A. Entropy

B. Enthalpy

C. Volume

D. Internal Energy

Click for Answer/Explanation

Correct Answer is C

Check by applying the Steady Flow Energy Equation (SFEE)

17. A heat engine is supplied with 2512 kJ/min of heat at 650 °C. Heat rejection with 900 kJ/min takes place at 100 °C. This type of heat engine is –

A. Ideal

B. Impossible

C. Irreversible

D. Practical

Click for Answer/Explanation

Correct Answer is C

Check by finding η.

Actual efficiency cannot be more than Carnot efficiency.

18. Molal specific heats of an ideal gas depend on-

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A. its temperature

B. its pressure

C. both its temperature and pressure

D. the number of atoms in a molecule

Click for Answer/Explanation

Correct Answer is D

Check by finding η.

Actual efficiency cannot be more than Carnot efficiency.

19. A Carnot engine operates between 327 °C and 27 °C. If the engine produces 300 kJ of work, the entropy change during heat addition is –

A. 0.5 kJ/K

B. 1 kJ/K

C. 1.5 kJ/K

D. 2 kJ/K

Click for Answer/Explanation

Correct Answer is B

20. For heat engine operating on the Carnot Cycle, the work output is 1/4th of the heat transferred to the sink. Find the efficiency (η) of the engine?

A. 20%

B. 30%

C. 40%

D. 60%

Click for Answer/Explanation

Correct Answer is A

Use Formula –

Work = 1/4 Q (rejected)

where Work = Q (added) – Q (rejected)

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