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Politics : The Environmentalist Thread -- Ignore unavailable to you. Want to Upgrade?

To: HPilot who wrote (19645)	1/15/2008 5:07:42 PM
From: neolib	Read Replies (2) \| Respond to of 36921

You seem confused, or at least your description is. Joules is just one unit to measure heat and energy. It can be used to measure work but that is usually measured in Watts or Horse Power. Wrong once again. Joule is the SI units measure of energy. "Heat" and "Work" are both "Energy", hence measured in Joules. Watts and Horse Power are Power not Energy. Power = Energy/unit time. Slight difference, but rather important. Regarding other units of measure, sure, there are systems besides the SI Units. But Energy does not equal Power in any of them. I am not sure what you are saying heat is only an energy flow, it only flows from hot to cold, work can move energy both directions. Heat is transferred energy caused by flow, which you are correct to note is due to temperature differences. Work is energy transferred by mechanical means, and may or maynot be reversible. There are also energy changes caused by chemical changes (combustion). The field of thermodynamics is concerned with ALL energy flows which affect temperature. That is why when you look at the equations based on the laws of thermodynamics you see all those different terms, some of which are heat, some are mechanical (pressure/volume change) and some are chemical related (number or moles, etc). There are also lots of different socalled potential energy measures defined for systems, to account for all these terms. BTW, does "Heat Transfer" ever strike you as odd terminology? It always has me, because the technical definition of "Heat" is that it is energy transferred by thermal gradients. Hence "Heat" implies transfer, so Heat Transfer seems redundant. At least it always has to me. We don't use the term "Work Transfer" for example, yet Work and Heat both are energy that is transferred. I think this is why T.P. confused Heat with Enthalpy. Its a little hard to define the temporal properties of heat. Before it is transferred it is part of Enthalpy in one body, and afterwards it is part of Enthalpy in the formerly cooler body. So heat is kind of an accounting term that can be used to say X amount of Enthalpy was transferred over Y amount of time, but the heat itself does not "exist" at one time. I think lots of people don't understand that difference. Just my approach to keeping it clear, FWIW.