| MadSci Network: Physics |
Walter, Most glasses are a solid solution of silicates and metal oxides http://glassproperties.com/glasses/ Glasses are usually ionic solids, however, the ions are immobilized and cannot conduct electricity by ionic conduction. http://en.wikipedia.org/wiki/Electrical_conduction Electrical conduction requires that charged particles be able to move thru the material. [It also requires a source of electrons and an anode and cathode reaction for ionic conduction] These particles are usually electrons in conductors such as metals or semiconductors. Solid state ionic compounds such as common salt, NaCl, or glass are usually insulators until either the ions are dissolved in a solvent such as salt water or molten as in melted salts or molten glass, or, if the material has semiconductor properties, a higher temperature increases electrons in a conduction band and therefore increases conduction. Pure salts usually have a sharp melting point with a rather abrupt increase in conductivity. Glasses, being a mixture and almost a very viscous liquid, will show a more gradual increase in conductivity. Finally if the applied voltage is high enough to cause dielectric breakdown any material will become a conductor. Descriptions of simple ionic conduction can be found in most general science texts or basic chemistry texts. A local high school science teacher might be willing to give some demonstrations to your classes. Regards, JimG
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