A real pendulum with friction will oscillate for a while after a short push but will eventually come to rest close to a location where is potential energy has a minimum. If the system is closed, that means, without a source of energy, it will eventually stop moving at a location near a minimum of the potential, no matter what type of friction force acts on the pendulum. This “variation principle” is a simple concept to predict the long-term behavior of mechanical systems, even if the details of the friction forces are unknown.
For many years, scientist tried to find a similarly simple variation principle for systems with a source of energy such as a periodic forcing function or a battery in electrical systems . Prigogine suggested that time rate of entropy production is at a minimum at stationary states . Later the concept of entropy was generalized and used to describe the dynamics and stationary states of open dissipative systems [3-7].
Which forces reduce entropy production?