How Does the Seebeck Effect Work in Thermoelectric Devices?
The Seebeck effect is a major observation in the study of physics. It is widely used in the application of semiconductors and conductors, and thus, has a lot of practical applications for us in our daily lives. German physicist Thomas Jonahan Seebeck was the one who formulated this, when he noticed that a magnetic compass, when brought in close proximity of two semiconductors can undergo a variation.
In short, the Seebeck effect explains the relationship between changes in temperature and semiconductors.
What Is The Seebeck Effect?
In 1821, German physicist Thomas Seebeck had observed the properties of the thermoelectric effect. It was seen that a circuit that had two different metals developed an EMF when their junctures were maintained at different temperature levels. These non-similar metals form what is known as a thermocouple, and the current that passes through this circuit is known as thermoelectric current.
The Seebeck effect explained the production of an electromotive force and the electric current in a loop of materials consisting of at least two dissimilar conductors maintained at two different temperatures, known as the thermocouples. It can be termed as the Seebeck effect thermocouple.
The Seebeck effect is a reversible process. If the hot and cold junctions are interchanged then the direction of the current will also change. Therefore, the thermoelectric effect is a reversible process. The magnitude and sign of thermo EMF depend on the materials of the two conductors and the temperature of the hot and cold junction.
Seebeck after discovering thermal properties of different pairs of metals arranged in series is called thermoelectric series. The thermoelectric effect is the conversion of temperature differences into electrical potential differences or vice versa using a thermocouple.
The Seebeck effect is the best example of an electromotive force. Through the Seebeck effect, we can also calculate the measurable electric currents or voltages in the same way as electromotive forces.
The local current density can be calculated using the formula,
⇒ J = σ(-ΔV + \[E_{emf}\])
Where, ΔV - The potential difference developed
\[E_{emf}\] - Electromotive force
σ - The local conductivity
The electromotive force created will explain the Seebeck effect and the equation of electromotive force in terms of the Seebeck coefficient is given by,
⇒ \[E_{emf}\] = -SΔT
Where, S - The Seebeck coefficient
ΔT - The temperature gradient
The Seebeck coefficient implies that a certain potential is induced in the circuit per change in temperature. It should be remembered that the Seebeck coefficients can change with temperature and they are dependent on the composition of the conductor. Usually it has been noticed that at room temperature, the Seebeck coefficient ranges between -100V/K to 1000V/K.
What Are Some Applications Of the Seebeck Effect?
Due to the fact that this monitors the change in temperature with conductivity, it is very useful in a number of modern operations that require electricity and conductivity at differential temperatures. Some of the common applications of this property are:
It can be useful in thermoelectric generators, which are used in industries and power plants to not let residual heat go waste and harness that into electricity.
In the automobile industry as well, the Seebeck effect can have many applications. It can be used to employ a thermoelectric generator which will lead to less fuel wastage.
It is also useful in thermocouples which can measure the potential difference between two semiconductors. Thermophiles are thermocouples arranged in series, and the Seebeck effect can be seen there as well.
FAQs on Seebeck Effect Explained: Concepts, Formula, Uses
1. What is the Seebeck effect?
The Seebeck effect is a thermoelectric phenomenon where a voltage, or electromotive force (EMF), is generated when the junctions of a circuit made from two dissimilar electrical conductors (or semiconductors) are maintained at different temperatures. This direct conversion of a temperature difference into electrical energy is the fundamental principle behind thermocouples.
2. How is the Seebeck effect used in a thermocouple?
A thermocouple is a sensor that uses the Seebeck effect to measure temperature. It consists of two different metal wires joined at one end, called the measuring junction. When this junction is exposed to a temperature different from the other end (the reference junction), a small, predictable voltage is produced due to the Seebeck effect. This voltage is directly proportional to the temperature difference, allowing for precise temperature measurement.
3. What is the formula for the Seebeck effect?
The electromotive force (EMF) generated by the Seebeck effect is described by the formula: Eemf = -SΔT. In this equation:
- Eemf represents the electromotive force or voltage produced.
- S is the Seebeck coefficient, a property that depends on the pair of materials used.
- ΔT is the temperature difference between the hot and cold junctions of the conductors.
4. What are the main real-world applications of the Seebeck effect?
The Seebeck effect has several important practical applications, including:
- Thermocouples: Widely used as temperature sensors in industries, scientific labs, and even home appliances.
- Thermoelectric Generators (TEGs): These devices convert waste heat directly into useful electrical power. They are used in power plants, the automotive industry to improve fuel efficiency, and for powering remote systems like space probes.
- Seebeck Generators: Small-scale power sources that can operate independently by harnessing heat from various sources to generate electricity for low-power devices.
5. What is the primary difference between the Seebeck effect and the Peltier effect?
The Seebeck and Peltier effects are essentially inverse phenomena. The key difference is:
- The Seebeck effect describes the creation of a voltage from a temperature difference.
- The Peltier effect describes the creation of a temperature difference (heating or cooling at a junction) by passing an electric current through it.
6. Is the Seebeck effect a reversible phenomenon?
Yes, the Seebeck effect is a reversible process. If the hot and cold junctions of the thermocouple are interchanged, the direction of the thermoelectric current and the polarity of the generated EMF will also reverse. The fundamental relationship between temperature difference and voltage remains, but its direction changes.
7. Why must two dissimilar conductors be used to demonstrate the Seebeck effect?
Two dissimilar conductors are essential because different materials have unique thermoelectric properties, specifically their free electron densities and how they react to temperature. When a material is heated, electrons diffuse from the hot end to the cold end. In a circuit with two different materials, the rate of electron diffusion is different in each. This imbalance creates a net potential difference and drives a continuous current. If both conductors were the same material, the potentials generated would be equal and opposite, cancelling each other out and resulting in no net EMF.
8. How are the Seebeck, Peltier, and Thomson effects different yet related thermoelectric phenomena?
All three are related aspects of thermoelectricity but describe different interactions between heat and electricity:
- Seebeck Effect: A temperature difference across a junction of two dissimilar materials produces a voltage.
- Peltier Effect: A current flowing through a junction of two dissimilar materials causes it to either heat up or cool down.
- Thomson Effect: A current flowing through a single conductor with a temperature gradient along its length will either absorb or release heat.
9. What determines the magnitude and sign of the thermo EMF produced in the Seebeck effect?
The magnitude and sign (polarity) of the thermo EMF are determined by two main factors:
- The materials used: The choice of the two conductors is crucial. The difference in their individual Seebeck coefficients determines how much voltage is produced per degree of temperature change.
- The temperature difference: According to the formula Eemf = -SΔT, a larger temperature difference (ΔT) between the hot and cold junctions results in a greater magnitude of the EMF. The sign depends on which junction is hotter and the relative Seebeck coefficients of the materials.
10. Could Seebeck generators be a significant source of clean energy in the future?
Seebeck generators hold promise as a source of clean energy because they can convert waste heat from sources like car exhausts or industrial processes directly into electricity with no moving parts or emissions. However, their widespread, large-scale use is currently limited by the relatively low efficiency and high cost of thermoelectric materials. Significant advancements in materials science are needed to make them competitive with other clean energy technologies like solar or wind for powering homes or cities.
