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 created which cancels the external electric
field. But in the case of a dielectric, which has no free electrons, the
external electric field only realigns the charges so that an internal electric
field is produced. The magnitude of the internal electric field is smaller 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 1.52(b).
The uniform electric
field between the plates acts as an external electric field 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
of 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 +σb and –σb. These charges are
called bound charges. They are not free to move like free electrons in
conductors. This is shown in the Figure 1.52(b).
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. This is shown in Figure 1.53.
Related Topics
Privacy Policy, Terms and Conditions, DMCA Policy and Compliant
Copyright © 2018-2024 BrainKart.com; All Rights Reserved. Developed by Therithal info, Chennai.