Thermodynamics PDF Notes, Important Questions and Synopsis
- Thermodynamics deals with the exchange of heat between a body and the surrounding along with other processes accompanying it.
- The nature of heat and its relationship to mechanical work was studied by Joule.
- Thermal equilibrium implies that systems are at the same temperature.
- Internal energy of a system is the sum of kinetic energies and potential energies of the molecular constituents of the system. It does not include the overall kinetic energy of the system.
- Equilibrium states of a thermodynamic system are described by state variables. The value of a state variable depends only on the particular state and not on the path used to arrive at that state.
- Examples of state variables are pressure (P), volume (V), temperature (T) and mass (m). Heat and work are not state variables.
- Zeroth law of thermodynamics: Two systems in thermal equilibrium with a third system are in thermal equilibrium with each other.
- The first law of thermodynamics is based on the principle of conservation of energy.
∆U = ∆Q − P∆V
- Efficiency of a heat engine is the ratio of work done by the engine to input heat.
- If all the input heat is converted entirely to heat, then the engine would have an efficiency of 1.
- In a reversible process, both the system and its environment can be returned to their initial states.
- Spontaneous processes of nature are irreversible. The idealised reversible process is a quasi-static process with no dissipative factors such as friction, viscosity etc.
- A quasi-static process is an infinitely slow process such that the system remains in thermal and mechanical equilibrium with the surroundings throughout. In a quasi-static process, the pressure and temperature of the environment can differ from those of the system only infinitesimally.
- A heat engine is a device in which a system undergoes a cyclic process resulting in conversion of heat to work.
- The Carnot engine is a reversible engine operating between two temperatures T1 (source) and T2 (sink). The Carnot cycle consists of two isothermal processes connected by two adiabatic processes.
- The efficiency of the Carnot engine is independent of the working substance of the engine. It only depends on the temperatures of the hot and cold reservoirs.
- Efficiency of the Carnot engine is 𝜂 = 1 − TC/TH = 1 − (Temperature of cold reservoir/Temperature of hot reservoir).
- The efficiency of an engine is never more than that of a Carnot engine.
- Heat lost by a hot body = heat gained by a cold body
- Heat can flow from cooler surroundings into a hotter body (e.g. coffee) to make it hotter.
No heat engine can convert heat to work with 100% efficiency.
When Q < 0, heat is removed from the system.
When W > 0, work is done by the system.
When W < 0, work is done on the system.
JEE Main Video Lectures By ExpertsVIEW ALL
Units and MeasurementThis video explains the international unit system, parallax method of measuring large distances and estimating the diameter of a molecule.
Electric Charge - Part 1This video describes the concept of charge, conductors and insulators, and methods of charging insulators.
Units and MeasurementThis video explains significant figures, rules to identify significant figures and rounding off uncertain digits.
Gold Leaf Electroscope - Part 1This video explains the basic properties of electric charges.
Coulom's Law of Electric Force - Part 1This video describes Coulomb's law to calculate the force between any two point charges and the comparison between Coulomb's law and Newton's law of gravitation.
Motion in a Straight LineThis video explains the calculation of displacement and average velocity of an object.
Queries asked on Sunday & after 7 pm from Monday to Saturday will be answered after 12 pm the next working day.
- Physics and Measurement
- Laws of Motion
- Work, Energy and Power
- Rotational Motion
- Properties of Solids and Liquids
- Kinetic Theory of Gases
- Oscillations and Waves
- Current Electricity
- Magnetic Effects of Current and Magnetism
- Electromagnetic Induction and Alternating Currents
- Electromagnetic Waves
- Dual Nature of Matter and Radiation
- Atoms and Nuclei
- Electronic Devices
- Communication Systems