Process function
Encyclopedia
A process function, process quantity, or a path function is a physical quantity
that describes the transition of a system
from an equilibrium state to another equilibrium state. As an example, mechanical work
and heat
are process quantities because they describe quantitatively the transition between equilibrium states of thermodynamic systems. It depends on the heat done and how the state is reached.
Path functions depend on the path taken to reach one state from another. Different routes give different quantities. Examples of path functions include work
, heat
, and distance
.
Physical quantity
A physical quantity is a physical property of a phenomenon, body, or substance, that can be quantified by measurement.-Definition of a physical quantity:Formally, the International Vocabulary of Metrology, 3rd edition defines quantity as:...
that describes the transition of a system
System
System is a set of interacting or interdependent components forming an integrated whole....
from an equilibrium state to another equilibrium state. As an example, mechanical work
Mechanical work
In physics, work is a scalar quantity that can be described as the product of a force times the distance through which it acts, and it is called the work of the force. Only the component of a force in the direction of the movement of its point of application does work...
and heat
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
are process quantities because they describe quantitatively the transition between equilibrium states of thermodynamic systems. It depends on the heat done and how the state is reached.
Path functions depend on the path taken to reach one state from another. Different routes give different quantities. Examples of path functions include work
Work (thermodynamics)
In thermodynamics, work performed by a system is the energy transferred to another system that is measured by the external generalized mechanical constraints on the system. As such, thermodynamic work is a generalization of the concept of mechanical work in mechanics. Thermodynamic work encompasses...
, heat
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
, and distance
Distance
Distance is a numerical description of how far apart objects are. In physics or everyday discussion, distance may refer to a physical length, or an estimation based on other criteria . In mathematics, a distance function or metric is a generalization of the concept of physical distance...
.