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Chapter 12: Thermodynamics

NCERT Solutions for CBSE Class 10 Physics — 101 solved questions with detailed explanations.

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Solved Questions

Q1. In an adiabatic process:

Heat is constant
Temperature is constant
No heat exchange occurs
Pressure is constant

Difficulty: Easy · Topic: Thermodynamic Processes

Solution

Adiabatic process: Q = 0, no heat exchange with surroundings.

Q2. In an isothermal process for ideal gas:

Temperature remains constant
Pressure is constant
No heat exchange
Volume is constant

Difficulty: Easy · Topic: Thermodynamic Processes

Solution

In an isothermal process for ideal gas: Temperature remains constant.

Q3. In an isochoric process:

Temperature is constant
Volume remains constant
Pressure remains constant
No heat exchange

Difficulty: Easy · Topic: Thermodynamic Processes

Solution

In an isochoric process: Volume remains constant.

Q4. In an isobaric process:

Volume remains constant
Temperature is constant
Pressure remains constant
No work is done

Difficulty: Easy · Topic: Thermodynamic Processes

Solution

In an isobaric process: Pressure remains constant.

Q5. First law of thermodynamics is:

Conservation of charge
Conservation of momentum
Conservation of energy
Entropy always increases

Difficulty: Easy · Topic: Thermodynamic Processes

Solution

First law of thermodynamics is: Conservation of energy.

Q6. The efficiency of a Carnot engine operating between 127°C and 27°C is:

25%
50%
75%
100%

Difficulty: Easy-Medium · Topic: Carnot Engine

Solution

η = 1 - T_cold/T_hot = 1 - 300/400 = 1/4 = 25%. (Temperatures in Kelvin: 127+273=400K, 27+273=300K).

Q7. For an ideal gas undergoing isothermal expansion:

ΔU > 0
ΔU < 0
ΔU = 0
Q = 0

Difficulty: Easy-Medium · Topic: First Law

Solution

In isothermal process, temperature is constant. For ideal gas, internal energy depends only on T, so ΔU = 0.

Q8. The work done by an ideal gas in an isobaric expansion from volume V to 2V at pressure P is:

PV
2PV
PV/2
P/V

Difficulty: Easy-Medium · Topic: Work in Processes

Solution

W = PΔV = P(2V - V) = PV.

Q9. A Carnot engine operates between 400 K and 300 K. Its efficiency is:

20.0%
35.0%
50.0%
25.0%

Difficulty: Easy-Medium · Topic: Carnot Engine

Solution

η = 1 - T_c/T_h = 1 - 300/400 = 25.0%.

Q10. A Carnot engine operates between 500 K and 300 K. Its efficiency is:

80.0%
50.0%
40.0%
35.0%

Difficulty: Easy-Medium · Topic: Carnot Engine

Solution

η = 1 - T_c/T_h = 1 - 300/500 = 40.0%.

Q11. A Carnot engine operates between 600 K and 300 K. Its efficiency is:

45.0%
50.0%
25.0%
60.0%

Difficulty: Easy-Medium · Topic: Carnot Engine

Solution

η = 1 - T_c/T_h = 1 - 300/600 = 50.0%.

Q12. A Carnot engine operates between 800 K and 400 K. Its efficiency is:

45.0%
50.0%
60.0%
25.0%

Difficulty: Easy-Medium · Topic: Carnot Engine

Solution

η = 1 - T_c/T_h = 1 - 400/800 = 50.0%.

Q13. A Carnot engine operates between 1000 K and 500 K. Its efficiency is:

45.0%
25.0%
50.0%
60.0%

Difficulty: Easy-Medium · Topic: Carnot Engine

Solution

η = 1 - T_c/T_h = 1 - 500/1000 = 50.0%.

Q14. A Carnot engine operates between 550 K and 310 K. Its efficiency is:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η = (1 - Tc/Th)×100%.

Q15. A Carnot engine operates between 600 K and 320 K. Its efficiency is:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η = (1 - Tc/Th)×100%.

Q16. A Carnot engine operates between 650 K and 330 K. Its efficiency is:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η = (1 - Tc/Th)×100%.

Q17. A Carnot engine operates between 700 K and 340 K. Its efficiency is:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η = (1 - Tc/Th)×100%.

Q18. A Carnot engine operates between 750 K and 350 K. Its efficiency is:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η = (1 - Tc/Th)×100%.

Q19. A Carnot engine operates between 800 K and 360 K. Its efficiency is:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η = (1 - Tc/Th)×100%.

Q20. A Carnot engine operates between 850 K and 370 K. Its efficiency is:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η = (1 - Tc/Th)×100%.

Q21. A Carnot engine operates between 900 K and 380 K. Its efficiency is:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η = (1 - Tc/Th)×100%.

Q22. A Carnot engine operates between 950 K and 390 K. Its efficiency is:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η = (1 - Tc/Th)×100%.

Q23. A Carnot engine operates between 1000 K and 400 K. Its efficiency is:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η = (1 - Tc/Th)×100%.

Q24. A Carnot engine operates between 1050 K and 410 K. Its efficiency is:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η = (1 - Tc/Th)×100%.

Q25. A Carnot engine operates between 1100 K and 420 K. Its efficiency is:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η = (1 - Tc/Th)×100%.

Q26. A Carnot engine operates between 1150 K and 430 K. Its efficiency is:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η = (1 - Tc/Th)×100%.

Q27. A Carnot engine operates between 1200 K and 440 K. Its efficiency is:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η = (1 - Tc/Th)×100%.

Q28. A Carnot engine operates between 1250 K and 450 K. Its efficiency is:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η = (1 - Tc/Th)×100%.

Q29. A Carnot engine operates between 1300 K and 460 K. Its efficiency is:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η = (1 - Tc/Th)×100%.

Q30. A Carnot engine operates between 1350 K and 470 K. Its efficiency is:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η = (1 - Tc/Th)×100%.

Q31. A Carnot engine operates between 1400 K and 480 K. Its efficiency is:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η = (1 - Tc/Th)×100%.

Q32. A Carnot engine operates between 1450 K and 490 K. Its efficiency is:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η = (1 - Tc/Th)×100%.

Q33. Carnot engine: T_H=400K, T_C=200K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-200/400)*100=50.0%.

Q34. Carnot engine: T_H=400K, T_C=250K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-250/400)*100=37.5%.

Q35. Carnot engine: T_H=400K, T_C=300K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-300/400)*100=25.0%.

Q36. Carnot engine: T_H=400K, T_C=350K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-350/400)*100=12.5%.

Q37. Carnot engine: T_H=450K, T_C=200K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-200/450)*100=55.56%.

Q38. Carnot engine: T_H=450K, T_C=250K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-250/450)*100=44.44%.

Q39. Carnot engine: T_H=450K, T_C=300K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-300/450)*100=33.33%.

Q40. Carnot engine: T_H=450K, T_C=350K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-350/450)*100=22.22%.

Q41. Carnot engine: T_H=450K, T_C=400K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-400/450)*100=11.11%.

Q42. Carnot engine: T_H=500K, T_C=200K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-200/500)*100=60.0%.

Q43. Carnot engine: T_H=500K, T_C=250K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-250/500)*100=50.0%.

Q44. Carnot engine: T_H=500K, T_C=300K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-300/500)*100=40.0%.

Q45. Carnot engine: T_H=500K, T_C=350K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-350/500)*100=30.0%.

Q46. Carnot engine: T_H=500K, T_C=400K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-400/500)*100=20.0%.

Q47. Carnot engine: T_H=500K, T_C=450K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-450/500)*100=10.0%.

Q48. Carnot engine: T_H=550K, T_C=200K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-200/550)*100=63.64%.

Q49. Carnot engine: T_H=550K, T_C=250K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-250/550)*100=54.55%.

Q50. Carnot engine: T_H=550K, T_C=300K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-300/550)*100=45.45%.

Q51. Carnot engine: T_H=550K, T_C=350K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-350/550)*100=36.36%.

Q52. Carnot engine: T_H=550K, T_C=400K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-400/550)*100=27.27%.

Q53. Carnot engine: T_H=550K, T_C=450K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-450/550)*100=18.18%.

Q54. Carnot engine: T_H=550K, T_C=500K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-500/550)*100=9.09%.

Q55. Carnot engine: T_H=600K, T_C=200K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-200/600)*100=66.67%.

Q56. Carnot engine: T_H=600K, T_C=250K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-250/600)*100=58.33%.

Q57. Carnot engine: T_H=600K, T_C=300K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-300/600)*100=50.0%.

Q58. Carnot engine: T_H=600K, T_C=350K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-350/600)*100=41.67%.

Q59. Carnot engine: T_H=600K, T_C=400K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-400/600)*100=33.33%.

Q60. Carnot engine: T_H=600K, T_C=450K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-450/600)*100=25.0%.

Q61. Carnot engine: T_H=600K, T_C=500K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-500/600)*100=16.67%.

Q62. Carnot engine: T_H=600K, T_C=550K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-550/600)*100=8.33%.

Q63. Carnot engine: T_H=650K, T_C=200K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-200/650)*100=69.23%.

Q64. Carnot engine: T_H=650K, T_C=250K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-250/650)*100=61.54%.

Q65. Carnot engine: T_H=650K, T_C=300K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-300/650)*100=53.85%.

Q66. Carnot engine: T_H=650K, T_C=350K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-350/650)*100=46.15%.

Q67. Carnot engine: T_H=650K, T_C=400K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-400/650)*100=38.46%.

Q68. Carnot engine: T_H=650K, T_C=450K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-450/650)*100=30.77%.

Q69. Carnot engine: T_H=650K, T_C=500K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-500/650)*100=23.08%.

Q70. Carnot engine: T_H=650K, T_C=550K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-550/650)*100=15.38%.

Q71. Carnot engine: T_H=650K, T_C=600K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-600/650)*100=7.69%.

Q72. Carnot engine: T_H=700K, T_C=200K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-200/700)*100=71.43%.

Q73. Carnot engine: T_H=700K, T_C=250K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-250/700)*100=64.29%.

Q74. Carnot engine: T_H=700K, T_C=300K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-300/700)*100=57.14%.

Q75. Carnot engine: T_H=700K, T_C=350K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-350/700)*100=50.0%.

Q76. Carnot engine: T_H=700K, T_C=400K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-400/700)*100=42.86%.

Q77. Carnot engine: T_H=700K, T_C=450K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-450/700)*100=35.71%.

Q78. Carnot engine: T_H=700K, T_C=500K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-500/700)*100=28.57%.

Q79. Carnot engine: T_H=700K, T_C=550K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-550/700)*100=21.43%.

Q80. Carnot engine: T_H=700K, T_C=600K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-600/700)*100=14.29%.

Q81. Carnot engine: T_H=700K, T_C=650K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-650/700)*100=7.14%.

Q82. Carnot engine: T_H=750K, T_C=200K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-200/750)*100=73.33%.

Q83. Carnot engine: T_H=750K, T_C=250K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-250/750)*100=66.67%.

Q84. Carnot engine: T_H=750K, T_C=300K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-300/750)*100=60.0%.

Q85. Carnot engine: T_H=750K, T_C=350K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-350/750)*100=53.33%.

Q86. Carnot engine: T_H=750K, T_C=400K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-400/750)*100=46.67%.

Q87. Carnot engine: T_H=750K, T_C=450K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-450/750)*100=40.0%.

Q88. Carnot engine: T_H=750K, T_C=500K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-500/750)*100=33.33%.

Q89. Carnot engine: T_H=750K, T_C=550K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-550/750)*100=26.67%.

Q90. Carnot engine: T_H=750K, T_C=600K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-600/750)*100=20.0%.

Q91. Carnot engine: T_H=750K, T_C=650K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-650/750)*100=13.33%.

Q92. Carnot engine: T_H=750K, T_C=700K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-700/750)*100=6.67%.

Q93. Carnot engine: T_H=800K, T_C=200K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-200/800)*100=75.0%.

Q94. Carnot engine: T_H=800K, T_C=250K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-250/800)*100=68.75%.

Q95. Carnot engine: T_H=800K, T_C=300K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-300/800)*100=62.5%.

Q96. Carnot engine: T_H=800K, T_C=350K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-350/800)*100=56.25%.

Q97. Carnot engine: T_H=800K, T_C=400K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-400/800)*100=50.0%.

Q98. Carnot engine: T_H=800K, T_C=450K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-450/800)*100=43.75%.

Q99. Carnot engine: T_H=800K, T_C=500K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-500/800)*100=37.5%.

Q100. Carnot engine: T_H=800K, T_C=550K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-550/800)*100=31.25%.

Q101. Carnot engine: T_H=800K, T_C=600K. Efficiency:

Difficulty: Easy-Medium · Topic: Carnot

Solution

η=(1-600/800)*100=25.0%.

Other Chapters in Physics

Ch 1: Physical World Ch 2: Units & Measurements Ch 3: Motion in a Straight Line Ch 4: Motion in a Plane Ch 5: Laws of Motion Ch 6: Work Energy & Power Ch 7: System of Particles Ch 8: Gravitation Ch 9: Mechanical Properties of Solids Ch 10: Mechanical Properties of Fluids Ch 11: Thermal Properties of Matter Ch 13: Kinetic Theory Ch 14: Oscillations Ch 15: Waves

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