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Explain dielectrics in detail and how an electric field is induced inside a dielectric . |
Answer» Solution :Induced ELECTRIC field inside the dielectric : When an external electric field is applied on a CONDUCTOR the charges are aligned in such a way that an internal electric field is produced . The magnitude of the internal electric field is smaller than that of external electric field is SMALL than that of external electric field . Therefore the net electric field inside the dielectric is not zero but is parallel to an external electric field with magnitude less than that of the external electric field . For example let us consider a rectangular dielectric slab placed between two oppositely charged plates ( capacitor ) as shown in the figure . The uniform electric field between the plates acts as an external electric field `vecE_("ext") ` which polarizes the dielectric placed between plates . The positive charges are induced on one side SURFACE and negative charges are induced on the other side fo surface . But inside the dielectric the net charge is zero even in a small VOLUME . So the dielectric in the external field is equivalent to two oppositely charged sheets with the surface charge densities `+ sigma ` and `-sigma b`. These charges are called bound charges . They are not free to move like free electrons in conductors . This is shown in the figure .  For example the charged balloon after rubbing sticks onto a wall . The reason is that the negatively charged balloon is brought near the wall it polarizes opposite charges on the surface of the wall which attracts the balloon. |
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