állapotváltozói

Állapotváltozói, in English state variables, are a fundamental concept in various fields of science and engineering, particularly in thermodynamics and control systems. They are a set of minimum independent variables that completely describe the state of a system at any given time. Knowing the values of all state variables allows one to predict the future behavior of the system without needing to know its past history.

In thermodynamics, state variables include quantities such as temperature, pressure, volume, and internal energy. These variables are not independent of each other; for a given substance, there are relationships, like the ideal gas law, that connect them. The set of state variables chosen is typically the smallest number of variables that uniquely defines the system's thermodynamic state. For a simple compressible system, for instance, two independent intensive properties like temperature and pressure are sufficient to determine all other thermodynamic properties.

In the context of control systems and dynamical systems, state variables represent the internal state of the system. These variables capture all the information needed to predict the system's evolution over time. For example, in a mechanical system, the position and velocity of each component might be state variables. For an electrical circuit, the voltages across capacitors and currents through inductors often serve as state variables. The system's dynamics are then described by a set of differential equations that govern how these state variables change over time. The concept of state variables is crucial for analyzing system stability, designing controllers, and simulating system behavior.