 Welcome back. So we were discussing open systems where primarily the heat transfer was the main mechanism that was of interest. So in this small snippet, we will consider open systems where the work transfer is primarily of interest. So if one has to look at the engineering devices that fall under this category, those would be turbines where work is extracted or compressor, pumps, fans, where actually work is input into the device and what one does is that we will again draw an open system and show what is of importance and we will again consider a steady state operation and it will be left to our devices if we want to investigate something which is transient in nature. Now unlike the heat transfer devices, most of these work transfer devices have some specific symbols that have been conventionally associated with them and hence instead of drawing a strange shape for the open system, what I would do is I will draw a few shapes and mention where what kind of devices they normally represent. So for example, a turbine is represented as follows. So let me just write work transfer devices. This is one of the most common depiction of the turbine where we show an inlet here and an exit here and this is the work output that is expected from the turbine and this is one of the places where historically the nomenclature for W dot s comes about. Normally the turbine power, output power is fed to the generator via a shaft and this W dot s is supposed to represent a shaft power that is the useful power that we are or the useful work that we are getting out and that is one of the reasons that useful power or the work that we extract is normally labeled as W dot s. So in a turbine normally either gas or steam expands and hence we have this flow going from inlet to exit in this direction where we have shown an expanding device and this is the work transfer coming out and this is the exit of the turbine. Similarly, for a compressor one would draw as such it is just the reverse. So here we have drawn something which is converging in the sense that we are showing that you are compressing the air or steam that is being put in this is the inlet and exit. We have still drawn conventionally the work transfer as an outside arrow one should of course realize that it will be a negative number you actually put in work into the system. So this is compressor a pump is normally depicted by a circle though it performs the same duty as a compressor and one normally puts an arrow in the direction of pressure increase like this and shows an inlet I and an exit E and the work transfer W dot s. Sometimes for centrifugal pumps you would notice that the outside arrow is drawn radially out outward and that is some of the depiction of pumps you will see. So this is a pump. So we will consider the work transfer devices and how the open system looks for them in the next snippet. Thank you.