Thermal Machines: Carnot Cycle and Efficiency

This lecture covers the principles of thermal machines, focusing on the Carnot cycle, which consists of two isothermal and two adiabatic processes. The instructor explains the significance of the Carnot cycle in thermodynamics, illustrating how it operates in a pressure-volume (PV) diagram. Key concepts such as work done during isothermal and adiabatic processes, energy variations, and the relationship between heat and work are discussed. The lecture also addresses the Kelvin and Clausius postulates, emphasizing the impossibility of a monothermic machine and the natural direction of heat transfer. The efficiency of the Carnot cycle is derived, highlighting the importance of temperature differences between heat sources. The instructor further explores the Stirling engine as a practical application of these principles, demonstrating the cycle's operation and efficiency. The lecture concludes with a discussion on the limitations of real thermal machines compared to the idealized Carnot cycle, reinforcing the foundational concepts of thermodynamics.