what is polarisation dielectric slab
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Answer:
When an electric field is applied across a dielectric material then the dielectric material becomes polarized.This mechanism is called dielectric polarization.If you are not familiar with dipoles and polarization then gain some basic knowledge about those and then proceed with this answer.
There are four different mechanisms by which dielectric polarization occurs.
1.electronic polarization.
When the electric field is applied the cloud center of negative charges gets displaced (since electrons have less mass ).So, there is a small separation between the negative charge cloud center and positive charge cloud center.Inside the atom the valence electrons are more displaced than the electrons lying nearer to the nucleus.This can be understood from the fact that the energy required to remove valence electrons is 1ev.While, the energy required to remove inner most electrons is 10ev.
2.ionic polarization: This occurs in ionic solids.The individual ions are arranged in proper lattice sites.We can imagine them as arranged in linear structure. When no electric field is applied the net polarization is zero.when the electric field is applied the ions are attracted in opposite directions and there is some net dipole moment.
3.orientational polarization :
This occurs in solids where permanent dipoles already exist. When electric field is applied across a HCl molecule , the H+ ion and cl- ions are attracted in opposite directions .But, the strong covalent bond prevents the molecule from breaking off.So, the molecule experiences torque .This torque tries to rotate the molecule and align it in the direction of electric field.Due to thermal energy possessed by the molecules the dipilrs move randomly and collide with the other dipoles and with the walls of the container.
4.Interface polarization: This kind of polarization occurs when there is accumulation of charges in a region separating two materials .For e.g when a electric field is applied across the dielectric in a capacitor the electrons are attracted toward the positive electrode but they are not able to escape. So, there is a accumulation of electrons and positive charges surround it.This results in polarization. Similar kind of polarization occurs in heterogeneous crystals or crystals containing defects .Electrons are trapped in these defects and polarization charges are created in the defects. This gives rise to a polarization .
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