Explore topic-wise MCQs in Thermodynamics Questions and Answers.

This section includes 12 Mcqs, each offering curated multiple-choice questions to sharpen your Thermodynamics Questions and Answers knowledge and support exam preparation. Choose a topic below to get started.

1.

A piston cylinder contains 3 kg of air at 20°C and 300 kPa. It is now heated at a constant pressure to 600 K. Find the work in the process.

A. 244.2 kJ
B. 254.2 kJ
C. 264.2 kJ
D. 274.2 kJ
Answer» D. 274.2 kJ
Discussion
2.

A piston/cylinder contains 1 kg water at 20°C with volume 0.1 m3. While the water is heated to saturated vapour, the piston is not allowed to move. Find the final temperature.

A. 201.7°C
B. 211.7°C
C. 215.7°C
D. 221.7°C
Answer» C. 215.7°C
Discussion
3.

A piston/cylinder has 5m of liquid 20°C water on top of piston with cross-sectional area of 0.1 m2. Air is let in under the piston that rises and pushes the water out. Find the necessary work to push all the water out.

A. 62.88 kJ
B. 52.88 kJ
C. 92.88 kJ
D. 42.88 kJ
Answer» B. 52.88 kJ
Discussion
4.

A piston cylinder contains air at 600 kPa, 290 K and volume of 0.01 m3. A constant pressure process gives out 54 kJ of work. Find the final temperature of the air.

A. 2700 K
B. 2800 K
C. 2900 K
D. 3000 K
Answer» D. 3000 K
Discussion
5.

A piston-cylinder contains 0.1 kg saturated liquid and vapour water at 100 kPa with quality 25%. The mass of the piston is such that a pressure of 500 kPa will float it. The water is heated to 300°C. Find the work.

A. 2.91 kJ
B. 3.91 kJ
C. 4.91 kJ
D. 5.91 kJ
Answer» D. 5.91 kJ
Discussion
6.

Ammonia at 10°C with a mass of 10 kg is in a piston-cylinder arrangement with an initial volume of 1 m3. The piston initially resting on the stops has a mass such that a pressure of 900 kPa will float it. The ammonia is now slowly heated to 50°C. Find the work in the process.

A. 483.2 kJ
B. 583.2 kJ
C. 683.2 kJ
D. 783.2 kJ
Answer» C. 683.2 kJ
Discussion
7.

A piston-cylinder contains 1 kg of liquid water at 300 kPa, 20°C. Initially the piston floats, with a maximum enclosed volume of 0.002 m3 if the piston touches the stops. Now heat is added so that the final pressure is 600 kPa. Find the work in the process.

A. 0.30 kJ
B. 0.40 kJ
C. 0.50 kJ
D. 0.60 kJ
Answer» B. 0.40 kJ
Discussion
8.

Ammonia in a piston/cylinder arrangement is at 80°C, 700 kPa. It is now cooled at constant pressure to saturated vapour (state 2) at which point the piston is locked with a pin. The cooling continues to −10°C (state 3). Find the work.

A. -28.64 kJ/kg
B. -38.64 kJ/kg
C. -48.64 kJ/kg
D. -58.64 kJ/kg
Answer» C. -48.64 kJ/kg
Discussion
9.

A piston-cylinder contains 50 kg of water at 200 kPa with V=0.1 m3. Stops in the cylinder restricts the enclosed volume to 0.5 m3. The water is now heated to 200°C. Find the work done by the water.

A. 50 kJ
B. 60 kJ
C. 70 kJ
D. 80 kJ
Answer» E.
Discussion
10.

R-22 is contained in a piston-cylinder, where the volume is 11 L when the piston hits the stops. The initial state is 150 kPa, −30°C with V=10 L. This system warms up to 15°C. Find the work done by R-22 during this process.

A. 0.35 kJ
B. 0.25 kJ
C. 0.15 kJ
D. 0.05 kJ
Answer» D. 0.05 kJ
Discussion
11.

A piston-cylinder assembly has 1kg of R-134a at state 1 with 600 kPa, 110°C, and is then brought to saturated vapour, state 2, by cooling. The cooling continues to state 3 where the R-134a is saturated liquid. Find the work in each of the two steps, 1 to 2 and 2 to 3.

A. 0, -20.22 kJ
B. -20.22 kJ,0
C. 0, 0
D. -20.22 kJ, -20.22 kJ
Answer» B. -20.22 kJ,0
Discussion
12.

A cylinder contains 1kg of ammonia. Initially the ammonia is at 180°C, 2 MPa and is now cooled to saturated vapour at 40°C, and then further cooled to 20°C, at which point the quality is 50%. Find the total work for the process, assuming a linear variation of P versus V.

A. -19.4 kJ
B. -29.4 kJ
C. -39.4 kJ
D. -49.4 kJ
Answer» E.
Discussion