 Welcome back mechanical AI. A very essential part after the second law of thermodynamics is the concept of entropy. This makes us wonder, what is entropy? To know more about how the Kelvin Planck's and Clausius statements equivalence is achieved, check out the second part. Now in this third part of the series we begin with the Carnot's theorem. Carnot's theorem states that of all the engines operating between a given constant temperature source and a given constant temperature sink, none has an efficiency higher than a reversible engine. Also Clausius theorem states that the cyclic integral of DQ upon T for a reversible cycle operating between two equilibrium states I and F is equal to zero. This integral can be replaced as a sum of two integrals, one each for R1 and the other for R2, which can be rearranged as R1 equals negative of R2. Since R2 is a reversible path, we can simply flip the equation while changing the negative sign. Since R1 and R2 represent any two reversible paths, so the equation for R is independent of the reversible path connecting I and F, that is there exists a property of a system whose value at a final state minus its value at an initial state is equal to R. This property is called entropy and is denoted by S. Hence we learned about what the Carnot and Clausius theorem is. Then we went on to find out what entropy is and why it is a property of the system. So like, subscribe and comment with your feedback to help us make better videos. Thanks for watching. Also thanks a lot for those constructive comments. You help the channel grow. So here are the top mechanical EIs of our last videos. In the next episode of Mechanical AI, find out what are the applications of entropy principle.