Physics:Characteristic time

The characteristic time is an estimate of the order of magnitude of the reaction time scale of a system. It can loosely be defined as the inverse of the reaction rate. In chemistry, the characteristic time is used to determine whether the problem needs to be solved as an equilibrium problem or a kinetic problem.

• In various fields of physics and astrophysics, the characteristic time or relaxation time refers to the time needed for a system to relax under external stimuli.
  • The characteristic time or relaxation time (RC time constant) of a simple RC circuit is the time it would take the capacitor to discharge from 100% down to 36.8% (1/e), or charge from 0% up to 63.2% (1 − 1/e).
• In dielectric spectroscopy, it is the reciprocal of the characteristic frequency.

See also

• Half-life
• Relaxation, for relaxation time