Imagine an external field, even infinitely ordered, is applied to a real system at a finite arbitrary rate. Part of this energy, regardless of its uniformity, does not convert to work on average over finite-time ensemble measurements. This is partly due to the random motions of particles inside the system to different directions at a given temperature -in absolute zero Kelvin the entropy is zero as there is no kinetic energy for random motions of particles. In this regard, external energy dissipates into different degrees of freedom in the form of heat at a given temperature. Therefore, even for an idealized thermodynamic system in which there is no other pathway for wasting energy such as friction or resistance, still part of the external energy dissipate into kinetic energies of particles and heat through random motions. In a broader picture, these random motions altogether emerge as a resultant force that opposes the external force on the boundary and across the system. The difference between the energy that is applied to the idealized system and the work that is done on the system is referred to as the entropy of that system. The usable energy which is the portion of energy that converts to work in an idealized system is realized as the free energy of the system. It is because of the entropy gain that the macroscopic state of the nonequilibrium system changes with time's arrow through an irreversible process.