Closed system
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[edit] Thermodynamics
In thermodynamics, a closed system, as contrasted with an isolated system, can exchange heat and work, but not matter, with its surroundings. For a simple system, with only one type of particle (atom or molecule), this amounts to a constant number of particles. However, for systems which are undergoing a chemical reaction, there may be all sorts of molecules being generated and destroyed by the reaction process. In this case, the fact that the system is closed is expressed by saying that the total number of each elemental atom is conserved, no matter what kind of molecule it may be a part of. Mathematically:
where Nj is the number of j-type molecules, aij is the number of atoms of element i in molecule j and bi0 is the total number of atoms of element i in the system, which remains constant, since the system is closed. There will be one such equation for each different element in the system.
[edit] Toll road
For toll roads, a "closed system" refers to a road where a motorist obtains a ticket upon entering the toll road, then pays to toll upon exiting the expressway. The toll is calculated by the distance traveled on the toll road. In contrast, a toll road using an 'open system' consists of mainline toll plazas (a.k.a., toll barriers) at set intervals; it is possible for motorists to get on an 'open toll road' after one toll barrier and exit before the next one, thus traveling on the toll road toll-free. Most open toll roads have ramp tolls to prevent that.
[edit] See also
- Dynamical system: Has components and/or flows that change over time.
- Open system: Can be influenced by events outside of the actual or conceptual boundaries.
