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Thermodynamics - Lecture - 3

 THERMODYNAMIC EQUILIBRIUM

: a state of a physical system in which it is in mechanical, chemical, and thermal equilibrium and in which there is therefore no tendency for spontaneous change.

THERMODYNAMIC PATH 

is the path or series of states through which a system passes from an initial equilibrium state to a final equilibrium state and can be viewed graphically on a pressure-volume (P-V), pressure-temperature (P-T), and temperature-entropy (T-s) diagrams.

PROCESS

 The change of system from one state to other state is known as thermodynamic process.



REVERSIBLE PROCESS 

is one in which both the system and its environment can return to exactly the states they were in by following the reverse path.

An IRREVERSIBLE PROCESS is one in which the system and its environment cannot return together to exactly the states that they were in.



Heat

Heat is the form of energy that is transferred between two substances at different temperatures. Heat is measured in units of energy, usually calories or joules

Work

Work is the product of force and displacement. Work transfers energy from one place to another, or one form to another. The SI unit of work is the joule (J)


Displacement Work

Consider a piston cylinder arrangement as given in the Figure. If the pressure of the fluid is greater than that of the surroundings, there will be an unbalanced force on the face of the piston. Hence, the piston will move towards right.


SIGN CONVENTION

Heat Transfer To A System & Work Done By A System Are Positive

Heat Transfer From A System & Work Done On A System Are Negative.

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