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The Physics and Chemistry of Matter
- Thread starter David
- Start date
- Joined
- May 25, 2003
- Location
- galesburg illinois
cant believe it took me 2 weeks to find this now i have something to refer my friends too who are just starting to get into ocing.
great idea David and a truly valuable sticky to have around considering why were all here
great idea David and a truly valuable sticky to have around considering why were all here
- Joined
- Nov 9, 2004
Thanks David, very helpful!
-Sam
-Sam
David said:
I wanted to point out that P can be in any unit so long as you have the appropiate constant. In my chem class we did everything in Atmospheres (ATMs) so we used the Liter-Atmosphere(atm)-Mole-Kelvin constant for the Ideal Gas Law which is .08206. When doing these calculations make sure you either have the right constant or convert your units to match your constant. There are english system constants as well I believe.
You may want to add some values for R which can be found towards the bottom of this chart. That should allow the buding chemists of the forum to be more flexible
.
- Joined
- Feb 17, 2005
David said:
The quality of this post was awesome I have to contribute something.
Silver 419 W/m-k
copper 385 W/m-k
Aluminum 210 W/m-k
These two I added because sometimes they are used as plating.
Nickel 60.7 W/m-k
Chromium 69.1 W/m-k
And these because of use in thermal compounds:
Zinc Oxide 23.4 W/m-k
Boron Nitride 2-60 W/m-k depending on direction - Not sure about this one.
Aluminum oxide <30 W/m-k
Also some solders:
63% tin 37% lead (eutectoid) 50.9 w/m-k melt point: 183 deg C
Indium 52 Tin 48: 34 W/m-k melt point: 118 deg C
I don't know if these last two will be of use, but they're there for completeness. Hope that helps, and very well done
- Joined
- Aug 3, 2003
maybe an useful appendum...
The Peltier Effect
A typical TEC (thermoelectric cooler) is comprised of an array of semiconductor-metal junctions that has been cleverly engineered in such a way that there is a side that absorbs heat and a side that releases heat. This has led to the application of TECs in cpu cooling b/c they do a good job of absorbing heat from the cpu and displacing it somewhere else (usually a waterblock).
Any ways, back the the S-N junction (semiconductor-metal). First come some restrictions. In order for an S-N junction to experience the Peltier Effect, the conduction electrons in the semiconductor must exist at a higher energy level than the conduction electrons in the metal. Ok, so now the metal electrons are just chilling. They are in the lowest energy state available and cannot flow into the semiconductor. The reason they cannot flow into the semiconductor is that they encounter a potential "hill" at the junction. This hill comes from the fact that the semiconductor electrons exist at a higher energy level than the metal electrons (recall this is not true in general, just in this case). In order for the metal electrons to flow into the semiconductor, they need to increase their energy.
-enter Peltier-
If you apply a current across a S-N junction, these electrons somehow must overcome this potential barrier. How, you ask? They absorb energy from the phonons, of course! In other words, they absorb thermal energy from the lattice. Now that the electrons have gained this energy from the lattice, they can easily flow across the junction. Current flowing from metal to semiconductor results in heat absorption, and current flowing from semiconductor to metal results in heat radiation (remember, the current flows in the opposite direction of electrons).
So now, you take your clever little TEC, apply a current, and get the hot and cold sides.
Physics Disclaimer: the previous only applies to n-type semiconductors, for p-type simply reverse everything.
edit: corrections welcome!
The Peltier Effect
A typical TEC (thermoelectric cooler) is comprised of an array of semiconductor-metal junctions that has been cleverly engineered in such a way that there is a side that absorbs heat and a side that releases heat. This has led to the application of TECs in cpu cooling b/c they do a good job of absorbing heat from the cpu and displacing it somewhere else (usually a waterblock).
Any ways, back the the S-N junction (semiconductor-metal). First come some restrictions. In order for an S-N junction to experience the Peltier Effect, the conduction electrons in the semiconductor must exist at a higher energy level than the conduction electrons in the metal. Ok, so now the metal electrons are just chilling. They are in the lowest energy state available and cannot flow into the semiconductor. The reason they cannot flow into the semiconductor is that they encounter a potential "hill" at the junction. This hill comes from the fact that the semiconductor electrons exist at a higher energy level than the metal electrons (recall this is not true in general, just in this case). In order for the metal electrons to flow into the semiconductor, they need to increase their energy.
-enter Peltier-
If you apply a current across a S-N junction, these electrons somehow must overcome this potential barrier. How, you ask? They absorb energy from the phonons, of course! In other words, they absorb thermal energy from the lattice. Now that the electrons have gained this energy from the lattice, they can easily flow across the junction. Current flowing from metal to semiconductor results in heat absorption, and current flowing from semiconductor to metal results in heat radiation (remember, the current flows in the opposite direction of electrons).
So now, you take your clever little TEC, apply a current, and get the hot and cold sides.
Physics Disclaimer: the previous only applies to n-type semiconductors, for p-type simply reverse everything.
edit: corrections welcome!
- Joined
- Oct 16, 2003
This is an awesome sticky, I also have an answer for why is water the best solution for cooling.....
My physics teacher told me once that if you dont know the answer to a question about water, one sure way to increase your chance of getting the right answer is to say that ITS POLAR!
So, not that I dont know at all why water is better, but I just wanted to say because its Polar.
My physics teacher told me once that if you dont know the answer to a question about water, one sure way to increase your chance of getting the right answer is to say that ITS POLAR!
So, not that I dont know at all why water is better, but I just wanted to say because its Polar.
- Joined
- Oct 16, 2003
David said:You are more or less correct
Haha, Thanks. Ill have to let my Physics teacher know that his tip has been put to work and it turned out he was somewhat correct.
Once again, great post.
- Joined
- Aug 30, 2004
- Location
- Dayton, OH
Now we need a Quantum Mechanics sticky from supernade.
- Joined
- Sep 25, 2004
- Location
- Orlando, Fl
nice, Sticky
- Joined
- Nov 24, 2001
- Location
- Dallas, Georgia
Can we get a mod in here to delete this guy.Seems his french is limited to one link in ALL the threads he has posted in.
That of course would be the above c3dlc .
That of course would be the above c3dlc .
- Joined
- Nov 24, 2001
- Location
- Dallas, Georgia
Donny_Paycheck is on it.
I like Donny, another old timer.
I like Donny, another old timer.
- Joined
- May 29, 2004
Might want to add a note about network solids like SiO2 and the like
A beautiful sticky indeed
A beautiful sticky indeed
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