Internal Energy of A Closed Thermodynamic System
This above summation of all components of change in internal energy assume that a positive energy denotes heat added to the system or work done on the system, while a negative energy denotes work of the system on the environment.
Typically this relationship is expressed in infinitesimal terms using the differentials of each term. Only the internal energy is an exact differential. For a system undergoing only thermodynamics processes, i.e. a closed system that can exchange only heat and work, the change in the internal energy is
which constitutes the first law of thermodynamics. It may be expressed in terms of other thermodynamic parameters. Each term is composed of an intensive variable (a generalized force) and its conjugate infinitesimal extensive variable (a generalized displacement).
For example, for a non-viscous fluid, the mechanical work done on the system may be related to the pressure p and volume V. The pressure is the intensive generalized force, while the volume is the extensive generalized displacement:
- .
This defines the direction of work, W, to be energy flow from the working system to the surroundings, indicated by a negative term. Taking the direction of heat transfer Q to be into the working fluid and assuming a reversible process, the heat is
- .
- is temperature
- is entropy
and the change in internal energy becomes
Read more about this topic: Internal Energy
Famous quotes containing the words internal, energy, closed and/or system:
“No real “vital” character in fiction is altogether a conscious construction of the author. On the contrary, it may be a sort of parasitic growth upon the author’s personality, developing by internal necessity as much as by external addition.”
—T.S. (Thomas Stearns)
“Just as we are learning to value and conserve the air we breathe, the water we drink, the energy we use, we must learn to value and conserve our capacity for nurture. Otherwise, in the name of human potential we will slowly but surely erode the source of our humanity.”
—Elaine Heffner (20th century)
“Because you live, O Christ,
the spirit bird of hope is freed for flying,
our cages of despair no longer keep us closed and life-denying.
The stone has rolled away and death cannot imprison!
O sing this Easter Day, for Jesus Christ has risen!”
—Shirley Erena Murray (20th century)
“Nobody is glad in the gladness of another, and our system is one of war, of an injurious superiority. Every child of the Saxon race is educated to wish to be first. It is our system; and a man comes to measure his greatness by the regrets, envies, and hatreds of his competitors.”
—Ralph Waldo Emerson (1803–1882)