Equilibrium

For the science fiction film, see Equilibrium (2002 film)

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Equilibrium or balance is any of a number of related phenomena in the natural and social sciences. In general, a system is said to be in a state of equilibrium if all influences on the system are cancelled by the effects of others. A related concept is stability; an equilibrium may or may not be stable.

• Some examples from the physical sciences:
  • Thermodynamic equilibrium, the state of a system in which its internal processes cause no net change in its macroscopic properties (such as temperature and pressure).
  • Chemical equilibrium, the state in which a chemical reaction proceeds at the same rate as its reverse reaction, resulting in no net change in the amount of each compound.
  • A system is in mechanical equilibrium when the sum of the forces on each particle of the system is zero.
  • The weighing instrument balance relies on an equilibrium.
  • In electronics, a balanced signal is also called a differential signal.
• Some examples from the biological and social sciences:
  • Physical balance of humans and animals is maintained with the aid of the sense of balance, and in special cases with a balance beam.
  • Psychologically some balance between desires and satisfaction is important; somewhat paradoxically complete satisfaction may not be ideal, it can be argued that perhaps it is better if things are left to be desired.
  • An addiction is any of various forms of unbalanced behavior.
  • In economics, static equilibrium and general equilibrium
  • Nash equilibrium in game theory, an optimum strategy for all players in a game, in the sense that no one player can benefit by changing his strategy while all other players keep theirs the same.
  • Reflective equilibrium in ethics, a state in which the consequences of one's general principles are consistent with one's opinions about individual cases.
  • For individuals and organisations a balance between income and expenses is often important, especially in the long run.
  • In various practical matters an equilibrium is useful, e.g. in a conversation, between talking and listening, or in a personal relationship, between giving and taking.
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