Objective: Record characteristics for various thermocouples and determine their sensitivity
If the ends of a metal wire are at different temperatures, since the thermally generated motions of the electrons have different velocities, thermal diffusion will occur between the hot and cold ends of the wire. The current resulting from this diffusion causes the cold end to be negatively charged with respect to the warmer end. The thermal diffusion voltage that arises is proportional to the difference in temperature between the two ends with the constant of proportionality being known as the Seebeck coefficient. If wires of two different metals are joined together, with contact points held at different temperatures, and a voltmeter is connected between the two unjoined ends, the result is a thermocouple. The voltmeter will then display a voltage which is directly proportional to the difference in temperature between the contact points. The experiment investigates this phenomenon with three different combinations of metals.