21-02-2012, 12:14 PM
DIELECTRICS AND MAGNETIC MATERIALS
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Insulators
Some materials like glass, ceramic, polymers and papers are non-conducting materials.
They prevent flow of current through them.
They provide electrical insulation.
DIELECTRICS
the non-conducting materials when placed in electric field modifies the electric field and themselves undergo appreciable change are called dielectrics.
Energy Band Diagram
The forbidden gap Eg is very large for dielectric.
Excitation of e- from the normally full valance band to empty conduction band cannot occurs.
Conduction cannot occur even when dielectric contains impurities.
Resistivity ranges from 1010 to 1020 ohm-m.
