Generally speaking, if a material system changes from one state to another and goes through different physical processes, although the initial state and the final state may remain the same, they may not be the same in the process
Many problems studied in physics are directly related to the whole process of a certain physical phenomenon, or some states in the process.Accordingly, many process quantities describing some physical processes and state quantities describing some specific physical states are introduced.
Conceptual differentiation
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The difference between process quantity and state quantity is that process quantity corresponds to time change quantity, while state quantity corresponds to time.
Process quantity is the physical quantity that an object can complete over a period of time, such as work, average speed, etc. It corresponds to the time interval!State quantity is the performance quantity of an object at a certain time, such as instantaneous speed, instantaneous power, etc. It corresponds to the time.
The relationship between them is that process quantity must determine the change quantity of state quantity.
State quantityThey are not isolated from process quantities, but closely related to each other. For example, the rate of work is power, the rate of change of distance is speed, and the rate of charge transfer is current.
State quantity: the integral of this quantity for any closed loop is zero, or the change of this quantity after any process is only related to the initial and final state, not the process path.Process quantity: there is a closed loop whose integral is not zero, or its change after a process depends not only on the initial and final states, but also on the process path.Typical state quantity:position，energy，volume，density，speed，acceleration，temperature，entropy, scalar potential, etc;Typical process quantity:distance, work, heat, etc.
