7/21/2019 Isolated System

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 Isolated System

An isolated system is more restrictive than a closed system as it does not interact with its

surroundings in any way. Mass and energy remains constant within the system, and no energy

or mass transfer takes place across the boundary. As time passes in an isolated system,

internal differences in the system tend to even out and pressures and temperatures tend to

equalize, as do density differences. A system in which all equalizing processes have gone

 practically to completion is in a state of  thermodynamic equilibrium.

It is important to note that isolated systems are not equivalent to closed systems. Closed

systems cannot echange matter with the surroundings, but can echange energy. Isolated

systems can echange neither matter nor energy with their surroundings, and as such are only

theoretical and do not eist in reality.

Thermodynamically isolated system

 !he internal energy of a thermally isolated system may therefore change due to the echange

of work energy. !he entropy of a thermally isolated system will increase in time if it is not at

equilibrium, but as long as it is at equilibrium, its entropy will be at a maimum and constant

value and will not change, no matter how much work energy the system echanges with its

environment. !o maintain this constant entropy, any echange of work energy with the

environment must therefore be quasistatic in nature, in order to assure that the system

remains essentially at equilibrium during the process.

An isolated system obeys the conservation law that its total energy"mass stays constant.