ABSTRACT
The first law of thermodynamics for a system undergoing a cyclic process states that the net heat and net work interactions are equal. Since the energy is transferred to an ordered mode of energy of the system, it can be converted entirely into work, which is also an ordered form of energy. Irrespective of the process used to convert the heat to work, the resultant change in the thermodynamic state of the system demands a certain amount of work to be transferred to the system to return it to its initial state. Consequently, energy supplied in the form of heat cannot be entirely converted into work. It is important to note that the emphasis is on engines that accomplish the conversion continuously by means of a cyclic process. The forms of first law relate the work interaction and heat interaction to the changes in the internal energy or enthalpy of the working substance.
