Describe Electric Polarization Of Dielectrics?

Question

Describe Electric Polarization Of Dielectrics?

2 Answers

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Answer 1

The increase in the capacity of a capacitor due to presence of dielectric is due to electric polarization of dielectric. The dielectric consists of atoms and molecules which are electrically neutral on the average. They contain equal number of positive and negative charges. The distribution of these charges in the atoms and molecules is such that the center of the positive charge coincides with the center of the negative charge. When the molecules of dielectric are subjected to an electric field between the plates of a capacitor, the negative charges (electrons) are attracted towards the positively charged plate of the capacitor and the positive charges (nuclei) towards the negatively charged plate.

The electrons in the dielectric (insulator) are not free to move but it is possible that the electrons and nuclei can undergo slight displacement when subjected to an electric field. As a result of this displacement the center of positive and negative charges now no longer coincides with each other. One end of molecules shows a negative charge and the other end, an equal amount of positive charge but the molecules as a whole is still neutral. Two equal and opposite charges separated by a small distance are said to constitute a dipole. Thus the molecules of the dielectric under the action of electric field become dipoles and the dielectric is said to be polarized.

Answer 2

A dielectric is a substance which has positive and negatively charged particles existing in a way that the number of the negatively charged particle is equal to the positively charged particles and hence we have a neutral state of the material as such. A dielectric is a non conductor of electricity in its normal state but it supports any externally applied electric field. As mentioned earlier that it has both positive and negative charges in itself and all of these charged or polar molecules are in random direction, if an electric field is applied it will start exerting the electrostatic force on the polar molecules orienting them in a specific direction i.e. All the negative molecules will be oriented towards the positive terminal of the electric field and the positive molecules will be oriented towards the negative terminal of the field. This is called the polarization of a dielectric. It is a very common phenomenon happening in case of a capacitor where a positive and a negative plate act as the opposite terminals of the capacitor and in order to increase capacitance the dielectric is introduced between the plates. The plates of the capacitor will produce the electric field which will polarize the dielectric, as a consequence the dielectric will produce an opposite field thereby reducing the intensity of original field and hence capacitance is increased.