5D20.60 Glass Conducts Electricity

PURPOSE: To demonstrate the relation between resistivity and temperature

DESCRIPTION: A Pyrex glass rod is wired in series with 120 VAC from the wall socket and a small neon bulb. At room temperature the resistance of the Pyrex rod is in the trillions, if not quadrillions, of ohms and the bulb does not light. But heat the glass red hot with a propane torch and enough charge carriers are promoted to conduction bands to cause the bulb to light brightly. The resistance of the glass has decreased by some ten orders of magnitude!

SETUP TIME: Minimal

COMPONENT LIST:

    


  1.  Pyrex rod wired with sm. neon bulb		Set up on EM shelves


  2.   Propane Torch				Locked in Cage

SUGGESTIONS:

REFERENCES: 2122 4.1; PIRA 5D20.60

OTHER NOTES: One might make the point that insulators have plenty of charge-carrying electrons, but normally they are bound and cannot function as a "conduction gas" the way they do in metals. (Don't bring up carbon!)