1.1 Background Research
Thomas Johann Seebeck, [born Apr. 9, 1770, Tallinn, Estonia, Russian Empire—died Dec. 10, 1831, Berlin, Prussia (Germany)], German physicist who discovered in 1821 that an electric current flows between different conductive materials that are kept at different temperatures, known as the Seebeck effect. He discovered that if a copper strip was joined to a strip of bismuth to form a closed circuit, heating one junction induced a current of electricity to flow around the circuit as long as the difference in temperature existed. This remained true of any pair of metals, and his original experiment revealed that merely holding one junction by hand was adequate to produce a measurable current. (Britannica,2018)
The Seebeck effect is a phenomenon in which a temperature difference between two dissimilar electrical conductors or semiconductors produces a voltage difference between the two substances. (Vaidyanathan,2019)
When heat is applied to one of the two conductors or semiconductors, heated electrons flow toward the cooler one. If the pair is connected through an electrical circuit, direct current (DC) flows through that circuit. (Rouse, M.,2008)
A thermopile is an electronic device that converts thermal energy into electrical energy. It is composed of several thermocouples connected usually in series or, less commonly, in parallel.
A thermocouple is a thermoelectric device for measuring temperature, consisting of two wires of different metals connected at two points, a voltage being developed between the two junctions in proportion to the temperature difference. A thermopile is an electronic device that converts thermal energy into electrical energy. It is composed of several thermocouples connected usually in series or, less commonly, in parallel. Thermocouples operate by measuring the temperature differential from their junction point to the point in which the thermocouple output voltage is measured. Once a closed circuit is made up of more than one metal and there is a difference in temperature between junctions and points of transition from one metal to another, a current is produced as if generated by a difference of potential between the hot and cold junction.
Thermocouples can be connected in series as thermocouple pairs with a junction located on either side of a thermal resistance layer. The output from the thermocouple pair will be a voltage that is directly proportional to the temperature difference across the thermal resistance layer and also to the heat flux through the thermal resistance layer. Adding more thermocouple pairs in series increases the magnitude of the voltage output. Thermopiles can be constructed with a single thermocouple pair, composed of two thermocouple junctions, or multiple thermocouple pairs.
Thermopiles do not respond to absolute temperature but generate an output voltage proportional to a local temperature difference or temperature gradient. The amount of voltage and power are very small and they are measured in milli-watts and milli-volts using controlled devices that are specifically designed for such purpose. (Wikipedia contributors, 2019)
1.2 Research Questions
1. How does the temperature difference affect the voltage produced?
2. What is the temperature difference needed to produce any voltage?
3. Do the number of hot and cold junctions affect the amount of voltage produced?
1.3 Hypothesis
The hypothesis is when there are more junctions the Seebeck effect will produce more electricity.
Independent Variables: Number of Junctions
Dependent Variables: voltage produced
Controlled Variables: temperature difference, temperature of the hot and cold junctions.
Links for the hypothesis.
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