Heat is deposited at the other junction. The main application of the Peltier effect is cooling. However the Peltier effect can also be used for heating or control of temperature. In every case, a DC voltage is required. A single stage thermoelectric cooler can produce a maximum temperature difference of about 70 degrees Celsius. Thermoelectric coolers offer a myriad of benefits when traditional cooling methods are unsuited.
Additionally, thermoelectric coolers are environmentally safer than other cooling units in the market. Some benefits of using thermoelectric cooling in electronic devices include:. The Peltier Effect and Thermoelectric Cooling The Peltier effect is the phenomenon that a potential difference applied across a thermocouple causes a temperature difference between the junctions of the different materials in the thermocouple.
This effect is the opposite of the Seebeck effect named after the scientist who discovered it in The Seebeck effect is that if different metals are connected in two separate places, and the intersections are kept at different temperatures, then a potential difference between the "junctions" the intersections will result. 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. 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? I apologize for more questions. 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. 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.
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