THERMODYNAMICS

(NEET, JEE, EAMCET)

Definition:-

Thermodynamics is the branch of science, which deals with heat and work and those properties which are related to heat and work.

(or)

A fascinated branch of science which deals energy, Entropy and Equilibrium (3E’S)is called Thermodynamics.

Energy:-The capacity to do any activity is called energy.

According to Thermodynamics, energies are mainly two types:

  1. High-grade energy (it can be completely converted to another form of energy)

 Ex: Mechanical energy, Electrical Energy, Hydraulic energy, Wind energy, etc.

  1. Low-grade energy (it cannot be completely converted to another form of energy)

Ex: Heat energy, Internal energy and geothermal energy.

Entropy:-The loss of something due to disorderness is called Entropy.

Entropy not only maintained by gases but also maintained by solids and liquids.

Equilibrium:-The system is said to be under thermodynamic Equilibrium if it maintains thermal Equilibrium, mechanical Equilibrium, and chemical equilibrium.

Thermal Equilibrium:-No temperature difference in the system and between the system and surroundings.

Mechanical Equilibrium:- No force difference in the system and between the system and surroundings.

Chemical Equilibrium:- No chemical reaction in the system and between the system and surroundings.

***System:- A quantity of matter or a particular region of space.

Boundary:-An envelop encloses the system.

Surroundings:- Everything outside the system.

Thermodynamically, the boundary has no thickness.

The boundary may be either real type or imaginary type, and again the real and imaginary boundaries may be fixed type or movable type.

Types of Systems:-

  1. **Open system:- (both mas and energy crossing the boundary of the system).

Ex: Turbine, Pump, Boiler etc.

2. ***Closed system:- (Only energy is crossing the boundary of the system.)

Ex: Battery, Thermometer, Refrigerator etc.

3. **Isolated system:- (Neither mass nor energy crossing the boundary of the system).

Ex: Universe.

Thermodynamic state:- The condition of the system at any point of time or period of time is called TD State.

Ex. Solid-state, liquid state, vapour state, etc.

Process:- The change of state is called process. (Thermodynamic process may be either reversible or irreversible.)

  1. ***Reversible process:- The process is said to be reversible if it can be performed in the reverse direction exactly in the same manner as in the forward direction. (Represented by a thick line.)

Ex: Quasi static process.

  1. Irreversible process:- The process is said to be irreversible if it cannot be performed in the reverse direction exactly in the same manner as in the forward direction. (Represented by a broken line.)

Ex: All natural process and combustion process.

TD Cycle:- It consists of many number of the process, but both initial and final states are identical.

NOTE:- At least two processes are required to complete a thermodynamic cycle.

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