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.
Originally the pain was in a lot of places--jaw, neck, upper palatte, ear, teeth, face. I was treated for tmj which helped most of the pain. I was then sent to a neurologist. He says the electric shock was a very strong indicator that the nerve was hit and is now either permamently damaged or irritated (bruised). He says the fact that my pain is very localized in the third branch of the trigeminal nerve says to him it is not tmj anymore. Also, if one responds well to nerve medications but regular pain killers such as Advil or Tylenol do nothing, it is likely a nerve problem.