# Thermodynamics Notes, Class 11 Physics | SwaVid

Thermodynamics, NCERT Class 11 Physics: notes with key ideas, formulas, common mistakes and 3 quick checks with worked answers.

Canonical: https://www.swavid.com/cbse/class-11/physics/chapter/thermodynamics

Source: https://www.swavid.com/cbse/class-11/physics/chapter/thermodynamics

# Thermodynamics

## Formulas and definitions

## Key ideas

## Common mistakes

## Quick checks

## Keep going

## Questions parents ask

## Class 11 Physics on SwaVid

### Thermal equilibrium and zeroth law

### Internal energy, heat, and work

### First law of thermodynamics

### Specific heat capacities of gases

### Thermodynamic processes

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SwaVid › CBSE › Class 11 › Physics › Thermodynamics

Notes written by SwaVid from the NCERT textbook.

Class 11 Physics, Chapter 11. Key ideas, formulas and common mistakes.

CBSE prints 20 marks for Units VII-IX together, not for this chapter alone.

Short answer. This chapter deals with thermal equilibrium, heat, work, and the laws governing energy transfers in macroscopic thermodynamic systems. Students learn how internal energy changes through work and heat across various thermodynamic processes like isothermal, adiabatic, isobaric, and isochoric changes.

Source: NCERT Physics Part II (Reprint 2026-27) , Chapter 11, Thermodynamics

Two systems in thermal contact are in thermal equilibrium when their macroscopic variables do not change with time. The zeroth law states that if two systems A and B are each in thermal equilibrium with a third system C, they are also in thermal equilibrium with each other, which introduces the concept of temperature.

Internal energy is the sum of molecular kinetic and potential energies in the frame of reference where the centre of mass is at rest. Heat is energy transfer driven by a temperature difference, while work is energy transfer brought about by macroscopic mechanical means.

The first law is the general law of conservation of energy applied to any thermodynamic system. When heat ΔQ is supplied to a system, it equals the sum of the increase in internal energy ΔU and the work done by the system ΔW.

Gases have two principal molar specific heat capacities: Cp at constant pressure and Cv at constant volume. For an ideal gas, they satisfy Mayer's relation, Cp - Cv = R.

A quasi-static process is an infinitely slow process that keeps the system in thermodynamic equilibrium at every stage. Special cases include isothermal (constant temperature), adiabatic (no heat exchange), isobaric (constant pressure), and isochoric (constant volume) processes.

Try each question first. Then tap it to see the answer.

ΔQ = 250 J and ΔW = 110 J

ΔU = ΔQ - ΔW = 250 - 110 = 140 J

140 J

W = μ R T ln(V₂ / V₁)

W = 2 × 8.314 × 300 × ln(2.718 / 1.0)

W = 4988.4 × 1.0 = 4988.4 J

4988.4 J

W = P (V₂ - V₁)

W = 1.0 × 10⁵ × (0.05 - 0.02)

W = 1.0 × 10⁵ × 0.03 = 3000 J

3000 J

Kinetic Theory .

Thermal Properties of Matter .

The 14 chapters of Class 11 Physics .

CBSE does not give marks to one chapter. It prints 20 marks for Units VII-IX together (Properties of Bulk Matter; Thermodynamics; Behaviour of Perfect Gases and Kinetic Theory). Thermodynamics is part of that group.

No. They are written by SwaVid from the NCERT textbook. The CBSE curriculum is the reference for what is assessed.

Kinetic Theory.

SwaVid is an AI tutor for Indian students in Classes 6 to 12. It finds the earlier ideas a child missed, then teaches today’s chapter. Start free to see how it works.

- Ch 11 NCERT book
- 20 marks, Units VII-IX together
- 3 quick checks
- Using chemistry sign convention where work done on the system is positive . In NCERT Physics, ΔW is the work done by the system. Use ΔQ = ΔU + ΔW, so expansion has positive work and compression has negative work.
- Treating heat and work as state variables . Internal energy U is a state variable, but heat Q and work W depend on the path taken between states. Never write ΔQ as Q₂ - Q₁ or ΔW as W₂ - W₁.
- Assuming temperature is constant during an adiabatic expansion . In an adiabatic expansion, ΔQ = 0, so ΔU = -ΔW. Since the gas does positive work, internal energy decreases and temperature drops.
- Confusing T₁ and T₂ in the adiabatic work formula . Adiabatic work done by the gas is W = μ R (T₁ - T₂) / (γ - 1). Keep initial temperature T₁ first, or write it as (P₁ V₁ - P₂ V₂) / (γ - 1).

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