Thermodynamics
JKSSB Junior Engineer (Mechanical) · Thermal Engineering and Refrigeration & Air-conditioning · 52 practice questions with answers and explanations: 25 Easy, 27 Medium, 0 Hard.
Sample questions
Sample Easy question 1
A Mollier chart is a plot of:
- Pressure against volume
- Temperature against entropy
- Pressure against temperature
- Enthalpy against entropy
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Answer: D. It is the h–s diagram used for steam calculations.
Sample Easy question 2
Which of these is an extensive property?
- Pressure
- Volume
- Density
- Temperature
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Answer: B. Extensive properties depend on the size of the system.
Sample Easy question 3
The SI unit of entropy is:
- J/K
- W/K
- J·K
- J
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Answer: A. Entropy is heat divided by absolute temperature, in joules per kelvin.
Sample Medium question 4
A heat engine receives 500 kJ of heat and rejects 300 kJ to the sink. Its thermal efficiency is:
- 30 per cent
- 20 per cent
- 40 per cent
- 60 per cent
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Answer: C. Work = 500 − 300 = 200 kJ. Efficiency = 200/500 = 40 per cent.
Sample Medium question 5
For the same temperature limits, the COP of a heat pump is greater than the COP of a refrigerator by:
- 2
- 1
- it is the same
- 0.5
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Answer: B. COP(heat pump) = COP(refrigerator) + 1.
Sample Medium question 6
The ratio of specific heats γ for an ideal monatomic gas is about:
- 1.0
- 1.4
- 1.67
- 1.33
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Answer: C. For a monatomic gas, Cp = 5R/2 and Cv = 3R/2, so γ = 5/3 = 1.67.