2. Presentation Topic: QUASI STATIC PROCESS Presenting By: Mir Ali Hassan 16083386-001 Syed Mohsin Raza 16083386-002

3.  THERMODYNAMIC EQUILIBRIUM Equilibrium: A state of balance “A system is said to be in a state of thermodynamic equilibrium if the value of properties is the same at all points in the system.” Types of Thermodynamics Equilibrium Thermal Equilibrium Mechanical Equilibrium Chemical Equilibrium

4.  QUASI-STATIC PROCESS  Quasi static process is that process in which all the intermediate states are at equilibrium and the process is carried out infinitely slowly.  Let consider system of gas contained in cylinder.  The system initially is in an equilibrium state,and describe by properties p1,v1,T1.

5.  The upward force exerted by gas on the piston.  If the weights is removed, there will be unbalanced forced between the system and the surroundings.  Due to gas pressure, the piston will move up the stops.  Then system again comes to the equilibrium state which described by the properties p2,v2,T2.  But the intermediate state through by the system are non- equilibrium and it will not be possible to describe the path. Non-quasi-static processQuasi-static process

6. Non quasi-static process Quasi-static process (Fast expansion) (slow expansion) gas

7.  Thus process 1-2 is non-quasi-static process. It represent in dotted line on p-v diagram.  If above process 1-2 takes place slowly, then each step, there is only an infinitesimal (very small part) change in properties. It is possible, if single weight on the piston is replaced by number of many small pieces of weights.  These weight are removed one by one very slowly from the top of the piston.  If piston moved slowly, the molecule will have sufficient time to redistribute.

8. As a result, the pressure inside the cylinder will always be uniform and will rise at the same rate at all locations. So every state passed through all the equilibrium point is called ‘QUASI-STATIC PROCESS’ A quasi-static process is also called a reversible process. The main characteristic of this process is a succession of equilibrium states and infinite slowness.  Example Of quasi-static process 1) Iso-thermal process : Temperature constant 2) Iso-baric process : pressure constant 3) Iso-choric process : volume constant

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