The Seebeck effect is fairly linear; that is, the voltage produced by a heated junction of two wires is directly proportional to the temperature. This means that the temperature of the metal wire junction can be determined by measuring the voltage produced.
Causes[edit] Lightheadedness can be simply (and most commonly) an indication of a temporary shortage of blood or oxygen to the brain due to a drop in blood pressure, rapid dehydration from vomiting, diarrhea, or fever, or from playing a wind instrument.
Light-headedness often is caused by a momentary drop in blood pressure and blood flow to your head that occurs when you get up too quickly from a seated or lying position (orthostatic hypotension). Ongoing light-headedness may mean you have a more serious problem that needs to be evaluated.