Contact thermocouple electromotive force and the temperature difference electromotive force

Produced by the thermocouple thermoelectric emfs is composed of two parts of electromotive force: part two conductor contact electromotive force, the other part is a single conductor of temperature difference electromotive force. The following conductors as an example to show the generation of thermoelectric emfs. Magnetic flap U3y | | glass thermometer thermometer floating ball | | glass thermometer thermometer two-color thermometer

1. Contact electromotive force U3y magnetic flap | | glass thermometer thermometer floating ball | | glass thermometer thermometer two-color thermometer

when the conductor of A and B are two different materials, when in contact with both internal different number of free electrons per unit volume ( The electron density is different, respectively expressed in NA and NB) , therefore, the electrons in the diffusion rate is different in both directions. NA> NB, the conductor of A spread to conductor B than the number of electrons in A conductor B spread to A number of electronic conductor. So A conductor lose electronic positively charged, and electronic negatively charged conductor B. So, in A, B two conductor contact interface formed A field from A to B. The direction of the electric field and diffusion in the opposite direction, hinder the diffusion of continued. When diffusion effect and the spread of the block is equal, namely from the conductor to spread to the conductor B on the number of free electrons and under electric fields since the conductor B equals the number of free electrons spread to A conductor, the conductor is A state of dynamic balance. In this state, A and B two conductor contact potential difference is created, we call contact electromotive force. Magnetic flap U3y | | glass thermometer thermometer floating ball | | glass thermometer thermometer two-color thermometer

2. Temperature difference electromotive force U3y magnetic flap | | glass thermometer thermometer floating ball | | glass thermometer thermometer two-color thermometer

for conductor A or B, if its both ends respectively under different temperature field t, t0 ( t > t0） , inside the conductor, the hot end free electrons has a larger kinetic energy, so the move to the cold end, so that the hot end lose electronic positively charged, the cold end get electronic negatively charged. In this way, on both ends of a conductor, the hot end of a point to a static electric field on the cold side. The electric field to prevent further extension of the charge. In this way, the potential difference is produced on both ends of the conductor, called the potential difference of temperature difference electromotive force. U3y magnetic flap | | glass thermometer thermometer floating ball | | glass thermometer thermometer two-color thermometer

U3y magnetic flap | | glass thermometer thermometer floating ball | | glass thermometer thermometer two-color thermometer

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U3y magnetic flap | | glass thermometer thermometer floating ball | | glass thermometer thermometer two-color thermometer