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Q & A: dielectric

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Most recent answer: 10/22/2007
Q:
What is a dielectric medium?
- Anonymous
AZ
A:
Lots of materials are very poor conductors of electricity, because they have almost no charges free to move around very far. Nevertheless, every material has charges that can displace a little bit when bonds stretch under the influence of an electric field. So in addition to the field from the outside, there's an opposite field from all those slightly displaced electrons etc. Such materials (non-conducting) are called dielectrics.
At high frequencies of applied ac fields, the internal current flowing from those locally moving charges can exceed the currents from ordinary conduction even in materials like water, which is not a good insulator.

A dielectric medium is just one in which these dielectric effects are more important than long-range conduction. That includes lots of examples.
Mike W.

(published on 10/22/2007)

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