What is the thermoelectric effect

What is the thermoelectric effect

German physicist Sebek first discovered in 1821 that if the two metals are connected to a closed loop and the temperature of the two joints is different, the current is formed in the closed loop, which is called the thermoelectric effect or the Sebek effect. The current in the loop indicates that there exists electromotive force in the loop. The electromotive force due to temperature difference is called the thermoelectric force. The closed circuit that we weld to two different metals is called thermoelectric cell or thermocouple.

The size of the thermo electromotive force is only related to the properties of the two metals and the temperature at the joint. The electromotive force of the temperature difference of the metal is very small, such as the thermocouple made of copper and copper. When the temperature difference between the two joints is 100 degrees C, the electromotive force of the temperature difference in the loop is only 4.3mV.

When the current is formed in the thermocouple, the thermocouple joint placed at the high temperature heat source is absorbed from the high temperature heat source, while the other in the low temperature source is heated to the low temperature heat source. The difference between the heat absorption and exothermic of the two joints of the thermocouple is converted to the quantity of electric energy, and the power generation efficiency of the metal thermocouple is very low, about 0.1%, that is, heat. The electric couple absorbs 1000J from high temperature heat source, only 1J is converted into electric energy, and 999J heat is transmitted to low temperature heat source, so metal thermocouple should not be used as power supply. Its main purpose is to measure temperature as a thermometer.

In addition to the thermoelectric effect of metal, the semiconductor also has a thermoelectric effect. The thermoelectric cells made of some semiconductors have larger temperature difference electromotive force and higher power generation efficiency (6%~8%), so the semiconductor temperature difference battery can be used as a power supply in practice.