In thermodynamics, work is defined broadly, encompassing mechanical, electrical, and shaft work.
The most common form in piston-cylinder assemblies. The differential work is δW = P dV , where P is absolute pressure and dV is the change in volume. The total work is the integral of pressure with respect to volume: ( W = \int_1^2 P , dV ). The path of this process (isobaric, isothermal, adiabatic) determines the final work value. engineering thermodynamics work and heat transfer
For a closed system undergoing a cycle: [ \oint \delta Q = \oint \delta W ] The total work is the integral of pressure
While both represent energy in transit, their physical drivers are entirely different: Heat ( Rogers and Y.R. Mayhew
Even though the start and end points are identical, the energy transfer differs based on how the system got there. This distinguishes work and heat from thermodynamic properties like pressure or temperature, which are "state functions" (independent of path).
| Aspect | Work | Heat | |--------|------|------| | Driving potential | Force (pressure, torque, voltage) | Temperature difference | | Mechanism | Macroscopic, directional | Microscopic, random | | Convertibility to work | 100% convertible (in principle) | Limited by Carnot efficiency | | System boundary requirement | Often requires moving boundary or shaft | Requires temperature gradient | | Path dependence | Yes (area under ( p-V ) curve) | Yes (area under ( T-S ) curve) |
In the world of mechanical engineering, Engineering Thermodynamics: Work and Heat Transfer is often hailed as the "Bible" of the field . Originally written by G.F.C. Rogers and Y.R. Mayhew