In thermodynamics, the work done by a system during a quasi-static expansion or compression is defined as the pressure exerted times the change in volume (W = PΔV for infinitesimal steps, or W = ∫P dV over a finite process), which corresponds geometrically to the area under the process's path on a pressure-volume (PV) diagram. Because this area depends on the specific path taken between two macrostates, work is a path-dependent quantity rather than a state function, in contrast to internal energy, which depends only on the system's current macrostate (pressure, volume, temperature) and returns to its original value whenever the system returns to its original state regardless of the path traveled. This distinction between path-dependent process quantities (like work) and state functions (like internal energy) is a foundational concept in thermodynamics, underlying the analysis of cyclic processes where net work equals the enclosed area of a closed loop on the PV diagram.
In thermodynamics, the work done by a system during a quasi-static expansion or compression is defined as the pressure exerted times the change in volume (W = PΔV for infinitesimal steps, or W = ∫P d…