Quasistática

Quasistática is a term used in physics and engineering to describe a process that occurs slowly enough for the system to be considered in equilibrium at each intermediate step. This means that the changes happening within the system are so gradual that the system has time to adjust and maintain a state of thermodynamic or mechanical equilibrium throughout the entire process.

In a quasistatic process, the external conditions are altered infinitesimally. For example, in a thermodynamic quasistatic process, a gas might be compressed or expanded by applying or removing pressure in extremely small increments. This allows the temperature and pressure within the gas to remain uniform and essentially constant at any given instant, even as they change over time. Similarly, in a mechanical context, a quasistatic deformation would involve applying forces so slowly that internal stresses within the object redistribute themselves instantaneously.

The concept of quasistatics is an idealization. Real-world processes are never perfectly quasistatic, as there are always finite rates of change involved, leading to irreversible effects and deviations from equilibrium. However, the quasistatic model is a powerful tool for analysis. It simplifies complex problems by allowing the use of equilibrium thermodynamics and mechanics. Many important thermodynamic quantities, such as entropy changes, can be readily calculated for quasistatic processes. By approximating real processes as quasistatic, scientists and engineers can gain valuable insights and perform calculations that would otherwise be intractable. The key characteristic is the absence of significant gradients or disequilibrium states within the system during its evolution.