What is the physics behind the functioning of thermocouples?

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SUMMARY

The discussion centers on the physics of thermocouples, specifically the necessity of using two different metals to create a voltage through the thermoelectric effect. The thermoelectric effect relies on the diffusion of charge carriers, where impurities and lattice vibrations cause hot and cold carriers to diffuse at different rates, leading to a potential difference. Understanding this mechanism is crucial for conducting experiments involving thermocouples, as it directly impacts their functionality and efficiency.

PREREQUISITES
  • Understanding of the thermoelectric effect
  • Knowledge of charge carrier dynamics
  • Familiarity with concepts of impurities and lattice vibrations
  • Basic principles of electrostatics
NEXT STEPS
  • Research the thermoelectric effect in detail, focusing on charge carrier diffusion
  • Study the role of impurities and lattice vibrations in semiconductor physics
  • Explore the construction and materials used in thermocouples
  • Learn about the applications of thermocouples in temperature measurement
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Students and researchers in physics, engineers working with temperature sensors, and anyone interested in the principles of thermoelectric devices will benefit from this discussion.

krackers
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Hello there! I am planning to do an experiment on thermocouples but have a few questions.

1. What is the physics behind why the thermocouple works?

2. Why do two different metals need to be used for making this?

Thank you!
 
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No, I do not.

However, I did look through wikipedia and I think I might have found a section that pertains to my question. [http://en.wikipedia.org/wiki/Thermoelectric_effect#Charge-carrier_diffusion]

The part I am not clear on is this. [Taken from that article directly]

"If the rate of diffusion of hot and cold carriers in opposite directions is equal, there is no net change in charge. The diffusing charges are scattered by impurities, imperfections, and lattice vibrations or phonons. If the scattering is energy dependent, the hot and cold carriers will diffuse at different rates, creating a higher density of carriers at one end of the material and an electrostatic voltage."


Why would there be no potential difference if the rate of movement of the hot/cool electrons is equal? Why are two different metals necessary? Why would impurities, imperfections, lattice vibrations, or phonons make them diffuse at different rates, and how does that end up creating an electrostatic voltage?
 
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