Thermodynamics MCQ Set 4
THERMODYNAMICS MCQ SET 1
Q1. The total energy of a system is the sum of:
A) Heat and work
B) Internal, kinetic, and potential energy
C) Enthalpy and entropy
D) Flow work and pressure energy
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Answer: B) Internal, kinetic, and potential energy
Explanation: Total energy includes all forms of stored and moving energy in a system.
Q2. In steady flow process, which remains constant?
A) Pressure
B) Volume
C) Mass flow rate
D) Temperature
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Answer: C) Mass flow rate
Explanation: In steady flow, mass entering equals mass leaving the control volume per unit time.
Q3. The gas constant R for air is approximately:
A) 0.287 kJ/kg·K
B) 8.314 kJ/kg·K
C) 1.0 kJ/kg·K
D) 287 kJ/kg·K
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Answer: A) 0.287 kJ/kg·K
Explanation: R = 0.287 kJ/kg·K is used for air in thermodynamic calculations.
Q4. The process that occurs at constant temperature is called:
A) Isothermal
B) Isochoric
C) Isobaric
D) Adiabatic
Show AnswerAnswer: A) Isothermal
Explanation: In isothermal process, temperature remains constant throughout.
Q5. The change in internal energy of an ideal gas in an isothermal process is:
A) Zero
B) Positive
C) Negative
D) Maximum
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Answer: A) Zero
Explanation: Internal energy of an ideal gas depends only on temperature; if temperature is constant, ΔU = 0.
Q6. The amount of heat required to raise the temperature of 1 kg of a substance by 1°C is called:
A) Latent heat
B) Specific heat
C) Sensible heat
D) Enthalpy
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Answer: B) Specific heat
Explanation: Specific heat represents the energy needed to change the temperature of a unit mass by 1°C or 1 K.
Q7. The ratio of actual heat engine efficiency to Carnot efficiency is called:
A) Thermal efficiency
B) Relative efficiency
C) Mechanical efficiency
D) Volumetric efficiency
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Answer: B) Relative efficiency
Explanation: Relative efficiency = Actual efficiency / Carnot efficiency.
Q8. The amount of energy required to change a unit mass of solid into liquid is called:
A) Latent heat of fusion
B) Latent heat of vaporization
C) Specific heat
D) Heat of reaction
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Answer: A) Latent heat of fusion
Explanation: It’s the energy required to convert solid into liquid at constant temperature.
Q9. One ton of refrigeration equals:
A) 2.5 kJ/s
B) 3.5 kJ/s
C) 4.186 kJ/s
D) 210 kJ/s
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Answer: B) 3.5 kJ/s
Explanation: 1 ton of refrigeration = 3.517 kW = 3.5 kJ/s of cooling capacity.
Q10. COP of a refrigerator is always:
A) Greater than 1
B) Less than 1
C) Equal to 1
D) Zero
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Answer: A) Greater than 1
Explanation: Coefficient of Performance (COP) = QL/W; since heat extracted is more than work input, COP > 1.