Electrostatic Shielding
Dielectrics
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The Electrostatic potential is constant throughout the volume of the conductor and is equal to its value on surface .
Since , conductor has no tangential component ; no work is done in moving charge within conductor and on its surface . Hence the potential is constant .
Electrostatic Shielding
Electric field inside a cavity in a conductor is always zero . Even if the conductor is charged or charges are induced on a neutral conductor by an external field , all charges reside only on the outer surface of the conductor . Hence , the any cavity of any shape and size is always shielded from outer electric influence . This is called electrostatic shielding .
Dielectrics
Dielectrics are non-conducting substances having negligible number of charge carriers . In presence of an external electric field , dipole moments are induced in dielectrics by stretching and re-orienting the molecules of the dielectric . The collective dipole moment is the net charge on the surface of dielectric which opposes and reduces ( does not cancel ) the external field .