A low DC voltage is produced by the thermocouple when the two junctions are at different temperatures. This voltage is referred to as the thermoelectric voltage. This thermoelectric voltage is produced by the temperature gradient along the thermocouple wires.
Re: What's causes the electric shock type pain in a tooth Hi DM69. I'm not a dentist but I'm pretty sure its the erosion of your tooth exposing the pulp, I had the exact same feeling in my tooth before I had it extracted a month ago, so I feel your pain.
It may also occur as a result of gum recession and loss of the underlying cementum, which exposes the root surface. When dentin is exposed to an external stimulus, such as heat or cold, pressure, or sweet and sour foods and drinks, a person may feel discomfort and sometimes a sharp pain in the tooth or teeth.