THERMODYNAMICS MCQ SET 9
Q1. The air-standard cycle for a diesel engine is:
A) Otto cycle
B) Dual cycle
C) Diesel cycle
D) Joule cycle
Answer: C) Diesel cycle
Explanation: Diesel engines follow the Diesel cycle, having constant pressure heat addition.
Q2. The compression ratio in a petrol engine is generally:
A) 4 to 6
B) 6 to 10
C) 12 to 20
D) 20 to 30
Answer: B) 6 to 10
Explanation: Petrol engines operate with moderate compression ratios to avoid knocking.
Q3. The compression ratio in a diesel engine is generally:
A) 4 to 8
B) 8 to 12
C) 12 to 22
D) 22 to 30
Answer: C) 12 to 22
Explanation: Diesel engines require higher compression to achieve self-ignition of fuel.
Q4. The pressure of a gas is due to:
A) Weight of molecules
B) Molecular collisions with container walls
C) Volume of container
D) Nature of gas
Answer: B) Molecular collisions with container walls
Explanation: Pressure arises from molecular impacts per unit area of container walls.
Q5. The device used to measure the dryness fraction of steam is:
A) Manometer
B) Calorimeter
C) Thermometer
D) Pyrometer
Answer: B) Calorimeter
Explanation: A steam calorimeter measures the moisture content or dryness fraction of steam.
Q6. The dry saturated steam contains:
A) Water droplets
B) Superheated vapors
C) No water particles
D) Only vapor at high pressure
Answer: C) No water particles
Explanation: Dry saturated steam is at saturation temperature with no liquid present.
Q7. The process in which both heat and work interactions are zero is called:
A) Adiabatic process
B) Isolated process
C) Isothermal process
D) Isochoric process
Answer: B) Isolated process
Explanation: No energy crosses the boundary in an isolated process.
Q8. The main purpose of a regenerator in a gas turbine is to:
A) Cool the exhaust gas
B) Increase the mass flow
C) Recover waste heat
D) Reduce work input
Answer: C) Recover waste heat
Explanation: A regenerator transfers heat from exhaust gases to compressed air, improving efficiency.
Q9. The lowest temperature at which a substance can exist as a liquid is known as:
A) Critical temperature
B) Triple point
C) Freezing point
D) Minimum temperature
Answer: A) Critical temperature
Explanation: Above the critical temperature, a substance cannot exist as a liquid, no matter how high the pressure.
Q10. The area under a temperature-entropy (TโS) diagram represents:
A) Work done
B) Heat transfer
C) Pressure
D) Volume
Answer: B) Heat transfer
Explanation: On a TโS diagram, the area under the process curve equals heat transfer.
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