A Conversation for The Three Laws of Thermodynamics
tHREE LAWS OF THERMODYNAMICS.
The Cow Started conversation Nov 24, 2000
Where is the zeroth law? "Energy flows from hot to cold" ?
tHREE LAWS OF THERMODYNAMICS.
Martin Harper Posted Nov 24, 2000
I was told that the zeroth law was...
If A has more entropy than B and B has more entropy than C then A has more entropy than C.
But I could have misunderstood... 
tHREE LAWS OF THERMODYNAMICS.
The Cow Posted Nov 24, 2000
Maybe.
But it's basically physics legalese, just sealing off the loopholes.
tHREE LAWS OF THERMODYNAMICS.
Munchkin Posted Nov 24, 2000
I think they are the same thing, just said in different ways. I.e. If one thing is hotter than the other heat flows from hot to cold, but if they are the same temperature no heat flows. So, if no heat flows, they have the same energy. Also, if heat flows from A to B to C then A is hotter than B is hotter than C hence A has greater entropy than B has greater entropy than C. I've probably muddied the waters not end (I'm starting to confuse myself) but generally it is all the same mathematical thing just said differently.
tHREE LAWS OF THERMODYNAMICS.
Jake, the Tanguero - Muse of Salon Style Argentine Tango Posted Nov 25, 2000
*sigh*
Close but no cigar Munchkin. You are correct when you say that heat flows from hot to cold. And you are also correct when you say that when two objects have the same temperature, that heat flow ceases. However, the two objects do not have to have the same energy at the same temperature.
Here's an example. Suppose you take a one kilogram lump of iron, heat it up to 500 degrees Celsius and toss it into a 50,000 liter tank of water at 20 degrees Celsius. The two objects will swifty come to thermal equilibrium at about 20.000000000001 degrees Celsius or so. However, the amount of heat, as measured in calories, contained in the tank of water exceeds the amount of heat contained in the lump of iron by several orders of magnitude. If you suddenly transfered all of the heat from the water to the iron, the iron would vaporize nearly instantaneously. And that's because water has a HUGE specific heat relative to iron. It takes an awful lot of heat to make water hot, but not anywheres near as much heat to make iron hot. Heat is energy. Temperature is the rate of transfer of energy across a boundry, in other words, temperature is power.
Hope this helps.
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