Explain thermal electric effect and the thermocouple
The thermoelectric effect refers to the phenomenon of generating an electric current when there is a temperature gradient present between two different materials. This effect is based on the principle that a temperature difference creates a voltage difference, known as the Seebeck effect.
The Seebeck effect explains how a voltage is produced when two dissimilar metals are joined together, forming a junction. When there is a temperature difference between these two junctions, the electrons in the metal with higher temperature gain kinetic energy and move towards the colder junction. This results in the accumulation of positive charges at the colder junction and negative charges at the hotter junction, creating an electric potential difference or voltage.
A thermocouple is a device that utilizes the thermoelectric effect to measure temperature. It consists of two different metal wires, often referred to as thermoelements or legs, which are joined together at both ends to form two junctions. One junction is exposed to the temperature that needs to be measured, called the hot junction, while the other junction is kept at a reference temperature, known as the cold junction.
When there is a temperature difference between the hot and cold junctions of a thermocouple, an electric current is generated due to the Seebeck effect. This current is proportional to the temperature difference and can be measured as a voltage using a voltmeter. By calibrating the voltage output of a thermocouple with known temperature values, we can determine the temperature at the hot junction.
Thermocouples are widely used in various applications where temperature measurements are required, such as industrial processes, scientific experiments, and temperature control systems. They offer advantages like wide temperature range, fast response time, and robustness, making them suitable for both high and low-temperature measurements.