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Thermodynamics — Revision Notes

NIOS · Class 12 · Physics

Thermodynamics revision notes for NIOS Class 12 Physics: 4 topics in quick points. Part of the NIOS Class 12 Physics syllabus.

44 questions30 flashcards17 formulas & key relations5 concepts

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A pressure-temperature (P-T) phase diagram for water, showing the solid, liquid, and gas regions, the triple point, and critical point.
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Key Topics to Revise

1

Basic Concepts: Heat, Temperature, and Thermodynamic Systems

  • Heat is a form of energy that flows from a body at higher temperature to a body at lower temperature due to a temperature difference. It is NOT the same as internal energy.
  • Temperature is the property that determines whether two bodies are in thermal equilibrium. Two bodies in thermal equilibrium have the same temperature.
  • Unit of heat: 1 calorie = 4.18 Joules; 1 kcal = 1000 cal = 4180 J.
2

Thermodynamic Processes

  • Isothermal Process: Temperature is constant (ΔT = 0). Occurs in perfectly conducting cylinders. ΔQ, ΔU, and ΔW are all finite. For an ideal gas, ΔU = 0, so ΔQ = ΔW.
  • Adiabatic Process: No heat exchange (ΔQ = 0). Occurs in perfectly insulating cylinders. From First Law: ΔU = −ΔW. If gas is compressed, work is done ON the gas, ΔU increases (gas heats up). If gas exp
  • Isobaric Process: Pressure is constant (ΔP = 0). Example: Heating water under atmospheric pressure. Work done W = PΔV is non-zero.
3

Zeroth Law of Thermodynamics and Triple Point

  • Zeroth Law of Thermodynamics: If two bodies A and B are separately in thermal equilibrium with a third body C, then A and B are also in thermal equilibrium with each other.
  • The Zeroth Law introduces the concept of TEMPERATURE as a fundamental property. It is the scientific basis for thermometers.
  • Practical significance: A thermometer (body C) reads the same temperature when placed in contact with different bodies (A and B) that are in mutual thermal equilibrium.
4

Internal Energy and First Law of Thermodynamics

  • Internal Energy (U) is the sum of kinetic energy (random molecular motion) and potential energy (intermolecular forces) of all molecules in the system.
  • Internal energy is a STATE function — it depends only on the state (P, V, T) of the system, NOT on the path by which the state was reached.
  • Internal energy can be increased by: (1) Adding heat to the system, or (2) Doing work ON the system.

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Full Notes

Key Concepts

Heat is the form of energyA thermodynamic system is a definiteAn indicator diagram is a graphA system is in thermodynamic equilibriumFive major processes

Frequently Asked Questions

What are the important topics in Thermodynamics for NIOS Class 12 Physics?
Key topics in Thermodynamics include Basic Concepts: Heat, Temperature, and Thermodynamic Systems, Thermodynamic Processes, Zeroth Law of Thermodynamics and Triple Point, Internal Energy and First Law of Thermodynamics. Study these first, then practise questions on each for the NIOS Class 12 board exam.
How should I revise Thermodynamics for the NIOS Class 12 board exam?
Learn the core ideas first, then work through the 44 practice questions on Thermodynamics. Revise definitions regularly and use flashcards for quick recall before the exam.

Sources & Official References

Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.

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