 The last topic that we want to talk about in today's class is the idea of second law efficiency. If you recall, this is where we started the lecture. We said that thus far in the course we've looked at all the first law efficiencies, thermal efficiency, component or adiabatic efficiency. We said extra gene analysis enabled us to look at what we refer to as being a second law efficiency. So to write out a second law efficiency, this can be defined as being the thermal efficiency of the cycle that we're looking at divided by the thermal efficiency of a reversible cycle. So the second law efficiency can be defined as, so what we can say is that the second law efficiency is a ratio of the thermal efficiency of an actual heat engine to that of a reversible heat engine. Another way that we can write the second law efficiency is if we look at what extra g itself is. So another way to think about this in terms of extra g itself is the second law efficiency is the amount of extra g that we are able to recover divided by the amount of extra g that is supplied at a given state. So if we're going to examine extra g and we want to be able to determine the amount of extra g like we looked at when we looked at the temperature supply or the source of 1500 Kelvin, what we need to do is come up with a useful method of being able to quantify the extra g associated with different forms of energy, be it kinetic energy, potential energy, internal energy or the enthalpy or even heat transfer and work. So what we're going to spend a little bit of time in the next lecture looking at is a way to quantify different forms of energy as extra g types. So that is what we're going to be doing in the next lecture. We'll be taking a look at coming up with expressions for the extra g associated with different forms of energy. So with that I'll conclude this lecture and I'd like to thank you for your attention. Thank you, bye-bye.