Physics Van 3-site Navigational Menu

Physics Van Navigational Menu

Q & A: How can the Peltier effect work?

Learn more physics!

Most recent answer: 03/06/2015
Q:
I would like to know the basic physics of the Peltier effect. One source says heat has to be absorbed from environment in order to flow into the conductor of higher electrical energy(IEEE Trans Comp&Packaging Tech Vo.l28, no.2, 2005, 218-229). Wikipedia explains that "Depending on the magnitude of the current, heat must accumulate or deplete at the junction due to a non-zero divergence there caused by the carriers attempting to return to the equilibrium that existed before the current was applied by transferring energy from one connect to another". Other sources pretty much say the same thing. How can I explain this in layman's terms(I still don't understand it) (1)How doen electron gain energy from environment when flowing into conductor of higher energy? And,(2)How doen electron lose energy to environment when flowing into conductor of lower energy? Thank you very much in advance.
internet drug coupons coupons for prescription medications prescription coupon
married woman looking to cheat My wife cheated on me most women cheat
married men cheat with men why husbands cheat wifes cheat
abortion pill clinics abortion pill prices for abortions
coupons rx open www.januvia.com coupons
online discount pharmacy dotnetblogengine.net coupon for prescription
prescription drugs discount cards blog.plazacutlery.com coupons for viagra printable
viagra coupons free link drug coupons
manufacturer coupons for prescription drugs viagra 2016 coupon coupon prescription
can i take minocycline with birth control can i take minocycline with birth control can i take minocycline with birth control
viagra bestellen online viagra pillen kruidvat pillen kopen
diflucan 150 site diflucan sirup
kamagra wikipedia kamagra jelly kamagra shop
cefdinir red stool cefdinir nedir cefdinir nedir
voltaren retard voltaren forte voltaren spray
voltaren retard voltaren pomada voltaren spray
motilium enceinte blog.cr-inside.org motilium et grossesse
how expensive is an abortion abortion clinic abortion clinics dallas tx
vivitrol alcohol vivitrol implant narcan challenge

- Tony Hue (age 22)
Northridge, California
A:
This is a great question.

For background for other readers, the Peltier effect  is the electric-current-driven transfer of heat from one material to another. It's used in many little devices, including quiet no-moving-parts coolers.

Tony raises a really basic question. Why would electrons flow from a low-energy location to a high-energy location, absorbing energy from the environment? Shouldn't they flow "downhill" from the high-energy to low-energy location, dumping some energy to the environment, just like liquid water flows downhill?

Here's the secret: things don't always flow toward the lowest energy (E) place. They flow toward the lowest free-energy (F) place. F takes into account both energy and entropy (S): F=E-ST, where T is the absolute temperature. S is a measure of how many different microscopic states are available.

Thus if the high-energy place is also a place where adding an electron makes enough more S than it did in the low energy place, electrons flowing down the F slope will flow up the E slope. In order for that to happen, you need a junction of two different materials, so that the electron entropy is different in each part.

OK, that sounds way too abstract. In our analogy, is there any case where water flows up, soaking up energy from the environment? Yes, there certainly is. Think of when water evaporates. It flows up, gaining E, a little from gravity but mostly the energy required to break loose from the other molecules. However, it loses F because single molecules running around loose in the gas have much more S than do ones packed into a liquid.

Let's take the question one more step. Why do things tend to flow downhill in E in the first place? It turns out that the general rule is that nature seeks out as many states as it can get to, maximizing total S. If something flows downhill, it loses E, dumping that E into the environment. Heating up the environment increases its S.  Minimizing F turns out to be equivalent to maximizing the total S of the system plus its environment.

Mike W.
cheater click wifes who cheat
internet drug coupons coupons for prescription medications prescription coupon
married men cheat with men why husbands cheat wifes cheat
types of abortions site what happens when you get an abortion
free online coupons pharmacy coupon new prescription coupons
prescription drugs coupons viagra manufacturer coupon 2016 viagra coupon card
viagra coupons free read drug coupons
coupons prescriptions blog.brunothalmann.com manufacturer coupons for prescription drugs
cialis dosage and cialis dose for copd pts
where buy viagra online viagra for sale uk online viagra buy
cialis coupon lilly blog.nvcoin.com transfer prescription coupon
drug discount coupons blog.suntekusa.com discount coupons for prescriptions
coupons for prescriptions discount prescription coupons drug prescription card
lilly cialis coupon prostudiousa.com coupons prescriptions
discount prescription drug cards cialis online coupon prescription discounts cards
arcoxia 30 arcoxia 90 arcoxia wiki
champix alkohol go champix
sildenafil pfizer link sildenafil sandoz
seroquel 25 mg click seroquel debljanje
voltaren retard voltaren pomada voltaren spray
vivitrol alcohol vivitrol implant narcan challenge

(published on 08/04/2012)

Follow-Up #1: Peltier effect

Q:
Thank you very much for your kind and detailed answer!! Your answer sure helps a lot, but I have more questions. Entropy concept is too difficult for me. Could you please explain this again without involving the environment? I read from a source on the internet that electons travel at different speeds per material due to crystal orientation changes(Bridgman effect?). And that when electrons slow down, the junction becomes cool since the temperature represents the average speed of the particles. Is this explanation OK? Another explanation involving semiconductor is that electrons moving in one way and hole moving in the opposite way have different amount of energy. And that this creates energy flux from one semiconductor to another, either heating or cooling(a little vague for me). Could you please give comments and more explanation on these explanations? One last question is that does a junction gets hot(heat absorption?) or cold(heat rejection?)when current flows from n-type to p-type semiconductor? I apologize for more questions.
hillcrest abortion clinic site live abortion video
the best android phone link phone tracking apps
the best android phone link phone tracking apps
married men cheat with men why husbands cheat wifes cheat
types of abortions the weeks of pregnancy what happens when you get an abortion
best android spy spy on mobile how to spy on an android phone
walgreens coupons deals blog.mrwade.co.uk walgreens photo print coupons
married cheaters redsoctober.com dating for married men
discount card prescription damske.com print cvs
new prescription coupon viagra coupons printable prescription coupon card
new prescription coupon areta.se prescription coupon card
prescription discount coupons free prescription drug cards viagra discount coupons online
coupon for viagra viagra trial coupon viagra discount coupons online
can i take escitalopram in the morning link can i take escitalopram in the morning
viagra bestellen online viagra online shop pillen kopen
viagra bestellen online viagra online shop pillen kopen
augmentin générique read augmentin sirop
naprosyn roche rileytech.net naprosyn nedir
arcoxia 30 go arcoxia wiki
cialis open cialis walgreen coupon
allods online cwblog.centralworld.co.th allo allo
vivitrol alcohol vivitrol implant narcan challenge

- Tony Hue (age 22)
Northridge, California
A:
Hi Tony- I'm not sure I follow all of that, but here are some comments.
It's not really ok to say that the speed of the electrons gives the temperature. In metals, for example, most of the electrons travel very fast because there are so many that the slower-moving states all get filled up.  Even in materials where there are not so many electrons (not-too-heavily-doped semiconductors) the temperature is only related to the typical speed of random motions, not any speed of the systematic current.

With regard to the p-type and n-type, it may help to look at the picture in this article:

In equilibrium, with no current flowing, two opposite processes are in balance. Sometimes an electron and a hole will combine, releasing energy that heats up the material slightly. Sometimes an electron will absorb energy, popping free and leaving a hole. On the average then in each region the numbers of electrons and holes and the amount of thermal energy stays constant. However, in the n region where there are lots of fixed positive charges there are many more free electrons than holes. In the p region, with lots of fixed negative charges, there are a lot more holes than free electrons.

Now let's say you apply a little voltage to make current flow from n to p.  Since the electron charge is defined as negative. that means electrons in the n region are flowing away from the junction. Holes in the p region also flow away from the junction. Near the junction then the density of electron-hole pairs falls below the equilibrium value. So the process of electron-hole recombination releasing energy becomes less frequent there. The process of electron-hole formation absorbing energy continues unchanged. So that region is cooled.

What if you run current from p to n? Then electrons in the n region are carried toward the junction, as are the holes in the p region. You get a denser batch near the junction, increasing the recombination rate. So the junction heats up.

As you can see, in real Peltier devices the arrangement places all the junctions where the current flows from p to n on one side and the junctions where it goes from n to p on the other, pumping heat from one side to the other.

.Mike W.
why people cheat catch a cheat how many people cheat
the best android phone mealmixer.com phone tracking apps
married woman looking to cheat go most women cheat
married men cheat with men why husbands cheat wifes cheat
free prescription cards nwwebdesigns.net walgreens prints coupon codes
married cheaters redsoctober.com dating for married men
discount card prescription damske.com print cvs
rite aid prescription transfer coupon open coupon rite aid
diprolene site furosemide 40mg
diprolene go furosemide 40mg
free online coupons pharmacy coupon new prescription coupons
imitrex 50mg thyroxine flagyl 200mg
prescriptions coupons discount card for prescription drugs discount coupon for viagra
viagra coupons free softballspa.com drug coupons
cialis dosage and cialis dose for copd pts
cialis manufacturer coupon link prescription drug coupons
arcoxia 30 click arcoxia wiki
fluvoxamine (luvox) open fluvoxamina bula
nurofen cold and flu dosage internetsellout.com nurofen plus dosage
nurofen cold and flu dosage internetsellout.com nurofen plus dosage
prescriptions coupons coupons for prescriptions drug prescription card
prescriptions coupons coupons for prescriptions drug prescription card

(published on 08/05/2012)

Follow-Up #2: thermopower, Seebeck, electrons, and holes

Q:
Hi. I am asking on behalf of my 10 year old son. Well, I guess on my behalf since neither one of us can figure this out. He is researching thermoelectric generation with peltier tiles for a science fair project. The Seebeck Effect.I have read through several of your prior posts and am still not clear on a couple issues. I hope you can help.We remain confused about how the energy differential is converted to electricity. Our understanding of things so far is that the couples are of dissimilar metals because they are "doped" to have either an extra electron or extra hole (missing electron) making them more conductive to each other.Do the valence electrons and holes in the N and P doped pellets move away from the heat towards the cold (faster than movement in the opposite direction) because the energy is lower in the cooler part looking to find an energy equilibrium? (is this the following downhill you described in post https://van.physics.illinois.edu/qa/listing.php?id=19853&t=how-can-the-peltier-effect-work). So now that the electrons have moved to the cooler side that end is more negatively charged than the warm side? It is at this point that we have electric potential for a circuit?Also, the p and n doped pellets do not touch each other but are connected by another conductor on either side of the peltier tile. Are the valence electron and hole trying to find each other through the mutual conductive connection is that attraction creating the electric potential?Lastly and related to all of the above, we found this picture on Wikipedia (http://en.wikipedia.org/wiki/Thermoelectric_effect#mediaviewer/File:Thermoelectric_Generator_Diagram.svg) that suggests electrons and holes move away from the cold side to the warm side and there is only a connection between the pellets at the cold (presumably negative side). My son and I eagerly await your help with understanding these remaining issues. Of course I trust and hope that once he figures this out hell ask more question.Kind regards,PhilChicago
hillcrest abortion clinic site live abortion video
married men cheat with men open wifes cheat
free prescription cards go walgreens prints coupon codes
rite aid prescription transfer coupon open coupon rite aid
levitra pill go tadalafil pill
finasteride sigridw.com cialis 80mg
free online coupons onlineseoanalyzer.com new prescription coupons
imitrex 50mg thepoliticalsword.com flagyl 200mg
free viagra samples coupon open viagra 2016 coupon
prescription drugs coupons click viagra coupon card
coupons for prescriptions new prescription coupons prescription drugs discount cards
viagra coupon card blog.brunothalmann.com viagra free coupon
prescription discount coupons softballspa.com viagra discount coupons online
coupons prescriptions prescription savings cards manufacturer coupons for prescription drugs
can i take escitalopram in the morning link can i take escitalopram in the morning
can i take minocycline with birth control read can i take minocycline with birth control
can i take antabuse and naltrexone can i take antabuse and naltrexone can i take antabuse and naltrexone
cialis coupon card read cialis coupons from manufacturer
drug discount coupons link discount coupons for prescriptions
naproxennatrium zygonie.com naproxen migraine
voltaren ára house.raupes.net voltaren
kamagra wikipedia kamagra jelly kamagra shop
ibuprofen rapid ibuprofen spc ibuprofen
proscar vs propecia for hair loss proscar pris proscar pris
cialis open cialis walgreen coupon
voltaren retard voltaren pomada voltaren spray

- Phillip Torres (age 42)
Chicago
A:

Nice questions. Let's have a first crack at them, then you can come back for more clarification. Notice that in that image you cited (below) the electrons flow from hot to cold. So do the holes. The arrows in the circuit show the direction of current flow, which is the same as the hole-flow direction and opposite to the electron flow direction, because it happens that historically the electron charge got defined as negative.

"Thermoelectric Generator Diagram" by Ken Brazier - self-made, based on w:Image:ThermoelectricPowerGen.jpg by CM Cullen (which is GFDL 1.2 and CC-by 2.5 licensed). Licensed under GFDL via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Thermoelectric_Generator_Diagram.svg#mediaviewer/File:Thermoelectric_Generator_Diagram.svg

If the two parts (n and p) were separate, then the temperature difference would drive electrons to the cold end of the n part until the ordinary electrical potential between hot and cold ends in each becomes big enough to drive an equal current back the other way. The same thing happens with holes in the p part. The hot-to-cold electrical potentials in the n and p parts then have opposite signs, since it takes opposite signs of potential to drive negatively charged electrons and positively charged holes back toward the hot end. That's just what you figured out.

Now when you connect that external circuit, the simple electrical potential differences will cause electrons to flow in that circuit, assuming it's made of typical conductors. I think that's the process you describe as "the valence electron and hole trying to find each other through the mutual conductive connection".  Electrons arriving at the cold side of the p region do allow electron-hole recombination to occur there.

Here's another way to help think of it. Although entropy (S) isn't a conserved quantity, it can still flow around. The entropy flow will be from hot to cold. In the n part, the electrons are the thing that carries the entropy. In the p part, the holes carry the entropy.

I hope that helps your son get started.

Mike W.

hillcrest abortion clinic stories of abortion live abortion video
the best android phone link phone tracking apps
types of abortions site what happens when you get an abortion
free prescription cards nwwebdesigns.net walgreens prints coupon codes
finasteride zithromax cialis 80mg
imitrex 50mg site flagyl 200mg
online discount pharmacy dotnetblogengine.net coupon for prescription
prescription drugs discount cards blog.plazacutlery.com coupons for viagra printable
pfizer coupons for viagra prescription coupon viagra discounts coupons
lisinopril and energy drinks lisinopril and energy drinks lisinopril and energy drinks
acheter viagra pas acheter viagra pas acheter viagra pas
lilly cialis coupon click coupons prescriptions
augmentin générique arbot.cz augmentin sirop
naprosyn roche rileytech.net naprosyn nedir
arcoxia 30 arcoxia 90 arcoxia wiki
diflucan 150 site diflucan sirup
amlodipine 5 mg amlodipine bijwerkingen amlodipine accord
allods online cwblog.centralworld.co.th allo allo

(published on 03/05/2015)

Follow-Up #3: a thank you

Q:
Mike W., Thank you. Your explanation is very clear and I think in a format that a 5th grader can understand (something we'd just not been able to find yet).Many thanks and keep up the great work,Phil
why people cheat catch a cheat how many people cheat
married men cheat with men why husbands cheat wifes cheat
types of abortions site what happens when you get an abortion
ventolin 2mg bistromc.org deltasone 40mg
free online coupons prescription card new prescription coupons
prescription drugs coupons click viagra coupon card
viagra coupon card free prescription cards discount viagra free coupon
can i take escitalopram in the morning link can i take escitalopram in the morning
can i take minocycline with birth control read can i take minocycline with birth control
lisinopril and bisoprolol lisinopril and bisoprolol lisinopril and bisoprolol
where buy viagra online viagra for sale uk online viagra buy
claritinekombo read claritine za psa
niacine movidafm.net niacin v hrani
diflucan 150 site diflucan sirup
fluvoxamine (luvox) blog.tgworkshop.net fluvoxamina bula
cialis driverblog.suddath.com cialis walgreen coupon
cefdinir red stool cefdinir nedir cefdinir nedir
lasix injetavel lasix para emagrecer lasix
motilium enceinte motilium notice motilium et grossesse
cialis coupon card coupon prescription cialis coupon

- Phil (age 42)
Chicago, IL
A:

Thanks for the note!  The wiki images are a huge help in explainig things like this. We should use them more often.

Mike W.

p.s. Here's another old answer that might have something useful for you guys: .

why people cheat infidelity signs how many people cheat
types of abortions read what happens when you get an abortion
best android spy spy on mobile how to spy on an android phone
free prescription cards go walgreens prints coupon codes
priligy 30mg go cialis 40mg
free online coupons pharmacy coupon new prescription coupons
online discount pharmacy dotnetblogengine.net coupon for prescription
online discount pharmacy viagra coupons and discounts coupon for prescription
can i take escitalopram in the morning can i take escitalopram in the morning can i take escitalopram in the morning
cialis dosage and cialis dose for copd pts
diabetes affect sexuality diabetes sexuality treatment
acheter viagra pas acheter viagra pas acheter viagra pas
where buy viagra online side effects from viagra use online viagra buy
cialis manufacturer coupon cialis discounts coupons prescription drug coupons
cialis manufacturer coupon link prescription drug coupons
naprosyn roche rileytech.net naprosyn nedir
naprosyn roche naprosyn wiki naprosyn nedir
seroquel 25 mg click seroquel debljanje
buscopan hund buscopan wirkung buscopan dragees
amlodipine 5 mg link amlodipine accord
voltaren retard link voltaren spray
cialis coupon card evans.com.mx cialis coupon
vivitrol alcohol naltrexone alcoholism medication narcan challenge

(published on 03/06/2015)

Follow-up on this answer.