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Topic: thermodynamics question (Read 1109 times) |
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athenonrex
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thermodynamics question
« on: 2003-08-02 16:06:19 » |
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i cannot remember for the life of me the three laws of thermodynamics...could someone please help me out here. i think the second one has something to do with entropy, but it's a bit hazey..
danka,
athenonrex
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Hermit
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Re:thermodynamics question
« Reply #1 on: 2003-08-02 19:04:07 » |
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I'm not sure which "three laws of thermodynamics" you were looking for (Historical abberation or confusion with Newton's Three Laws of Motion perhaps?), but take your pick of these four :-)
The first law of Thermodynamics:Total energy of the system plus the surroundings is constant. Energy can neither be created nor destroyed. Energy is conserved.
For any process where heat Q is added to the system and work W is done by the system, the net energy Q-W equals this change 'delta' U in the internal energy of the system.
The second law of Thermodynamics:For an adiabatically enclosed system, the entropy can never decrease. Therefore, a high level of organization is very improbable.
In all processes some of the energy involved irreversibly looses its ability to do work. Thermodynamic entropy is the quantity of energy no longer available to do physical work: 'delta' S = or > 0. In any spontaneous process, 'delta' S, entropy, increases.
It is impossible that, at the end of a cycle of changes, heat has been transferred from a colder to a hotter body without at the same time converting a certain amount of work into heat.
The third law of thermodynamics:The asymptotic law, states that all processes slow down as they operate closer to the thermodynamic equilibrium making it difficult to reach that equilibrium in practice. 0 K can not be achieved.
The third law of thermodynamics states that the entropy of a pure perfect crystal is 0 at 0 K: 'delta' S(0K) = 0. There is a minimum disorder/energy in a pure crystaline solid at 0 K. [QM]
The fourth law of thermodynamics:If a system receives a through-flow of exergy (produce entropy/dissipate energy),- the system will utilize this exergy flow to move away from thermodynamic equilibrium,
- if it has more than one pathway to move away is offered from thermodynamic equilibrium, the one yielding most stored exergy, with the most ordered structure and the longest distance to thermodynamic equilibrium, will have a prospensity to be selected.
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With or without religion, you would have good people doing good things and evil people doing evil things. But for good people to do evil things, that takes religion. - Steven Weinberg, 1999
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localroger
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Re:thermodynamics question
« Reply #2 on: 2003-08-31 14:36:55 » |
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Quote from: athenonrex on 2003-08-02 16:06:19
i cannot remember for the life of me the three laws of thermodynamics...could someone please help me out here. i think the second one has something to do with entropy, but it's a bit hazey..
danka,
athenonrex
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As stated by C.P. Snow:
First Law: You can't win. (e.g. you can't get something for nothing, or create energy.)
Second Law: You can't even break even. (e.g. you can never get back to the state you're in now, because everything flows in a direction of increasing entropy.)
Third Law: You can't get out of the game. (e.g. you can't attain absolute zero.)
Of course this applies only to closed systems. The Earth is not a closed system, thanks to the existence of the Sun. The Solar System is pretty closed, though, and the Universe as a whole is considered to be completely closed, so in a few hundred billion years we're all toast unless we think of something, quick!
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the.bricoleur
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Re:thermodynamics question
« Reply #3 on: 2003-09-01 08:05:57 » |
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IMO, the heat-death of the universe is a fitting metaphor for spirituality.
the bricoleur
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Rhysenn
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Re:thermodynamics question
« Reply #4 on: 2003-11-24 00:18:53 » |
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the way i learned it, #2-4 were actually #1-3, and the law of conservation of energy was actually termed the zeroth law of thermodynamics, this because it had been assumed when the first three were created, but it was added as a law afterwards and was deemed to be the most fundamental.
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