 Sanjay Murt, Mechanical Engineering Department of Walsh and Institute of Technology at Sulapur. Today I am explaining regarding the thermodynamics video number four. The learning outcome of this video is student will able to discuss the path function and point function and the different parts of the work. So, what is the path function, what is the point function? In the previous lecture that video number three I am explaining regarding the thermodynamics process and cycle. Here it is one cycle, it is one loop and one more the graph I am showing one of the process that is here. The suppose the initial point here is the one process is to be there 1 a 2 and 2 b 1. So, 1 a 2 b 1 it is one loop that is called as a cycle. So, it is called as a one process one cycle. So, which path it will be followed that is very important when it moves from initial the arrow I am showing here. Suppose the initial point is to be there and it is a half part that is a one cycle that is a one a 2 and another half part is 2 b 1 means it moves from one complete cycle a b which path it will be followed half part is path followed by a and half part is path followed by b which path it will be followed that is very important because some what you call functions there depends on which path it will be followed. Suppose the simple example is to be there suppose you are moving from one destination to another destination through one path whatever the time required moving from one destination to the second destination that the two destination fix you are moving from your house to the school one and regular one path you can used it that path having term calculation is some 20 minutes to be there. But sometimes you can followed by different path it moves from you move from your house to the school by different path and the time calculation is different one. So, some are related to the path function and some are related to the point functions are there path functions are pressure volume temperature they are path function systems are to be there heat and work they are point functions are to be sorry they are heat and work they are to be point functions are to be there and which path it will be followed that will be very important one because when you have to calculate go for a heat and work the area under this curve we can define. Suppose heat you can calculate for this process the area under this curve you can calculate it. So, some characteristics are to be there that is heat and work they are related to the path functions are to be there and which are the point functions they are related to which path will be followed path a or path b or path c they are not related to which path it will be followed means initial condition the pressure p 1 volume v 1 temperature t 1 and here the second middle condition is the path p 2 path a is followed, but the values have to be changed p 2 v 2 t 2. So, p 1 to the p 2 they are not related which path will be followed they are to be end result they are related to the which are the state is there which is the equilibrium conditions are to be there. So, that is related to the point functions they are depends on the state only not how system it reaches that state in which that is a state a which path a is there path b is there path c is to be there path d is to be there from initial condition path e is to be there they are not related which path it will be followed these are called as a point functions are there which are a point functions pressure is there volume is there temperature is there it is to be there. So, these are to be related to the point functions are to be there another types another parameters they are related to the which path it will be followed means suppose it moves from 1 a 2 that is a work how to calculate the work that is a graph under this curve that is to be calculated here area under this graph that is to be important one means which path it will be followed that is to be very important that is are called as a point path functions are to be there. So, simple examples pressure volume temperature they are a point function they are related to the state related which where is a state where state functioning is to be there they are not related which path will be followed on the other end some characteristics of parameters are there that is a heat and work which are regularly used they are related to the path functions are to be there. Now, you go for a definitions of the what do you call work and heat work and heat is to be there. So, here I am showing work heat is a form of energy and work is amount of energy transfer is to be there heat and work also transformation of forms of energy from system to the surrounding and surrounding to the system one when heat is added to that system it is a positive one sorry heat is rejected from that system it is a positive one when heat is added that is a negative one you get the work from that system that is a positive one you have to supply the work that is a negative one some simple example is to be there suppose even your bike where petrol or diesel or fuel you get burned you get the what you call mechanical work from that system that is a positive on the other end when you have to go for a compressor is to be there to run that compressor you get the pressurized air you have to supply the work from that system. So, here work is a negative on the other end IC engineers the work is a positive one when you to go for a heat engine and heat pump heat engine you have to heat is rejected from lower side to the higher side and heat pump pumping action is to be going on. So, when you to go for heat you have to supplied for that system that is a negative you get the heat from that system that is a positive one. Now, what are the different types of works are to be there the first is the shaft work a paddle work is to be there means suppose what you call in your bicycle the motion is to be transmitted from this pocket and chain arrangement should be there. So, here work here to supplied for that by your foot arrangement you can transmit a work for that system and the bike or bicycle get starts running that is one type of work is to be there. Then PD work a piston cylinder arrangements should be there in that piston cylinder gas is there air is there some working substance is to be there when you have to add the heat for that expansion of the gas is going on. So, piston is going from level 1 to the level 2. So, whatever quantity of heat is to be added that is stored by its own energy internet but work is done how the work is done it moves from level 1 to the level 2 and that is to be stored that is a one type of the work is to be there. Electrical work is to be there suppose on closed chamber is to be there in that closed chamber the electric cable is to be transmitted and you have to supply the energy. So, the initially before supplying the energy electrical energy the temperature is T 1 we need to start the energy is the electrical is starting through that cable at wire the temperature of that room temperature of that gas is to be increased that is one type of work is to be there. So, magnetic work is to be there due to that magnetic rotations are to be going on some pendulums will be going from one end to the other end. So, due to the positive or negative due to the north pole and south poles are due to n and p poles are to you. So, working is to be going on that is a one type of work is to be there elongation work is to be there. Suppose, one cable is to be there you have to elongate that from another end one end to the other end that length is to be increases. So, this is a different type of the works are to be there. So, these are the different simple examples of the works are to be there. So, when you know the different type of the work when you know the definition of heat and work when you know the point function and a path functions when you know the definition of work and heat can you give some example of work is a positive or work is a negative heat is a positive or heat is a negative these examples you can regularly you can use it in the winter season in your house you can use the heater. So, what is the functioning what is the function of heat you get the work you get a warmer effect in your room or in the summer season you on the AC refrigeration system you on your AC machine you get a chilling effect cooling effect comfortable effect you get heat. So, here so, these are the examples of the heat added or heat rejected work is added or work is rejected in the what you call winter season heater is to be there in the heater you have to that you have to supply the electric energy and due to that electric energy the temperature of the room is to be increases through that cable through the wire through that coils. When you go for AC system in that AC system whatever the air to suck from that room pass through that condenser compressor systems. So, liquid to the gases form gases to the liquid form it is an a chilled effect and the what you call heated water is to be heated air is to be passed on that liquid it absorbs the heat and the temperature can absorb then whatever the comfortable low temperature again get circulated. So, these are the different type of works you can get. So, for this video I am taking a reference for a basic mechanical engineering book by R S Kurmi. Thank you.