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MIT Physics Demo -- Conducting Glass

A small glass tube, held by copper wire, is placed in series with a light bulb. The glass acts as an insulator at room temperature, meaning the current cannot flow between the copper wires. This leaves an open circuit and the light bulb does not light up. Touching a conductor across the copper wires (with a metal screwdriver for instance) does complete the circuit because it allows current to flow.

However, when glass is sufficiently heated by a torch it becomes an ionic conductor. Ionic bonds in the glass are broken, allowing the charge carrying ions to move freely. Thus, when the glass is melted the current can flow, which closes the circuit and lights the bulb.

Comments (1)

That is very interesting. I never learned that glass could be conductor.

Posted 6 years by Anonymous User

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MIT Department of Physics Technical Services Group

MIT Department of Physics Technical Services Group

Category: Science | Updated over 1 year ago

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June 20, 2008 15:47
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