In 1821, a well-respected German Physicist Johann Seebeck discovered that by forming a junction of two dissimilar metals, he was able to deflect a compass magnet. He thought at first that this was related to the Earth’s magnetic field. However it was later discovered that it was in fact caused by an electrical current, which was being generated and was flowing around the circuit. This current quickly became known as the thermoelectric force, and the effect which this had on voltage and temperature became known as the thermoelectric effect.
What is the Thermoelectric Effect?
The thermoelectric effect is a relationship formed between temperature and voltage. It is best exhibited with the use of metals.
When two metals are connected at a junction, a small voltage known as a thermoelectric voltage is created and a current is generated. This is because of the difference in energies being produced between electrons and ions in the metals.
Materials known to exhibit the thermoelectric effect are known as thermoelectric materials. They contain free electrons. When a temperature gradient is present between the electrons, the electrons at the hot end will move quicker than those at the cold end. Thus creating a small electro static force, which creates an electric potential to match the temperature gradient causing the movement of the electrons. This electrical potential energy is produced from a temperature difference during this process. This temperature difference can then be easily measured using a voltmeter.
Dependent on the temperature at which a reading is taking place, different types of metals are more suitable than others. As well as pure metals, alloys may also be used in certain assemblies.Thermally stable metals such as Nickel, Platinum and Rhodium, are commonly used in the production of high temperature sensors known as thermocouples.