I am learning the Carnot Cycle but I still get confused about this cycle. There are four steps in this cycle. 1)Isothermal expansion 2)Adiabatic expansion 3)Isothermal compression 4)Adiabatic compression After step one, we got the heat from heat reservoir through expansion but I don't understand how step 2 occur? Does it expand due to the remain heat in step 1? Also, do we need to do work in step 4 to finish this cycle?