Seebeck Effect: Invention, Explanation, and Application

Seebeck effect describes that a voltage differential can be created between two electrical conductors and/or semiconductors by varying their temperatures.

• The Seebeck effect, which occurs when two junctions are kept at different temperatures, results in the formation of an electromotive force (emf) and subsequently an electric current in a loop of material made up of at least two distinct conductors. 
• Although they are not required to be solids, conductors are frequently made of metals. Thomas Johann Seebeck, a German physicist, discovered the effect in 1821. 
• The Seebeck effect is used to produce electricity for certain applications as well as to detect temperature with high sensitivity and precision.

Key Terms: Seebeck Effect, Applications, Peltier, Thompson effect.

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Invention of Seebeck Effect

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In the year 1821, German physicist Thomas Seebeck made a number of thermoelectric effect observations. 

• The connection of two distinct metals with differing temperatures in a circuit was seen to produce an EMF. 
• When a closed loop was constructed between two dissimilar materials or semiconductors, he saw how the compass needle would deflect.
• A thermocouple is created from these several metals. The thermoelectric current that flows across this circuit is referred to as such.
• Earlier, it was thought that the magnetic field caused by temperature differences was what caused the compass needle to deviate, and he called this phenomenon the thermo-magnetic effect.
•  Eventually, Hans Christian Orsted understood that the current induced was the cause of the deflection.

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Explanation of Seebeck Effect

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The only ones accountable for Seebeck Effect is the valence electrons in the metal's hotter region, and thermal energy is the driving force behind this.

• Additionally, due to their high kinetic energy, these valence electrons move more quickly in the opposite direction—that is, toward the cooler end—than electrons moving from the warmer end to the colder end. 
• The Fermi distribution is acute on the cold side, meaning there are fewer electrons above Fermi energy, while it is soft on the hot side, meaning there are more electrons concentrated above Fermi energy.
• Moving from one end that is warmer to the other because electrons prefer lower energy areas causes energy to be transported, eventually bringing the temperature into equilibrium.
• A DC is generated as a result. 
• But for every Kelvin of temperature change, just a few microvolts (10-6) of voltage are generated. 
• Now that the voltage increases in series as well as the current increases in parallel, everyone is aware of this.
• So, bearing this in mind, if we can link many of these devices in series to increase the voltage or boost the maximum deliverable current, we should (in parallel). 
• Keeping in mind just that a significant temperature difference is necessary for this purpose.
• Current density is determined by:

J = σ (- ∇V + E_emf)

E_emf = – S∇T

• Where S is also known as the Seebeck coefficient or temperature gradient.
• The temperature affects the Seebeck coefficient. It is dependent on the conductor's makeup.
• For typical materials, the Seebeck coefficient varies from −100 μV/K to + 1,000 μV/K at ambient temperature.
• The system reaches steady-state when J=0, as well as the voltage gradient, is given by: \triangledown V = – S\ triangular down T.

Explanation of Seebeck Effect

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Application of Seebeck Effect

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The Seeback effect has several uses, including:

• The thermocouple Seebeck effect is frequently utilized to activate the electrical switches that can switch the device on or off or to assess temperature variations. Constantan and metals like copper, iron, chromium, and constantan are often used in thermocouple metal combinations.
• A thermoelectric generator, that serves as a heat engine, employs the Seebeck effect.
• These are also utilized in certain power plants to produce additional power from waste heat.
• As automotive thermoelectric generators in cars to improve fuel economy.

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Things to Remember

• When there is a temperature differential between various electrical conductors or semiconductors, the Seebeck effect refers to the accumulation of electric potential that results.
• Small voltages, typically only just a few microvolts (millionths of a volt) every kelvin of temperature differential at the junction in between conductors or semiconductors, are generated via the Seebeck effect.
• A few millivolts can be produced by some Seebeck-effect devices if the difference in temperature is significant enough (thousandths of a volt).
• Such devices can be coupled in parallel or series to raise their maximum deliverable current or voltage, respectively.
• If a significant temperature differential is maintained across the junctions, massive arrays of Seebeck-effect devices may produce useful, small-scale electrical power.