JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III Year ELECTRICAL ENGINEERING MATERIALS Previous Question Paper (March - 2021 - R16)

Dielectric polarization is the process of displacement of electric charges within a dielectric material when subjected to an external electric field, resulting in the formation of electric dipoles. The net dipole moment per unit volume is defined as the polarization vector, P.

Electronic polarization occurs in all atoms due to the displacement of the electron cloud relative to the positive nucleus. When an external field is applied, the center of the negative charge cloud shifts, creating an induced dipole moment proportional to the field strength. It is independent of temperature and occurs at optical frequencies.

Ionic polarization occurs in ionic crystals where positive and negative ions are displaced in opposite directions by an external electric field. This displacement changes the equilibrium distance between ions, resulting in a net dipole moment. It is typically slower than electronic polarization and is observed in the infrared frequency range.

Dielectric loss is the energy dissipated as heat within a dielectric material when it is subjected to an alternating electric field. This occurs because the dipoles cannot perfectly follow the rapid oscillations of the field, leading to internal friction and energy absorption.

The loss tangent, denoted as tan δ, is the ratio of the imaginary part of the complex permittivity (dielectric loss) to the real part (dielectric storage). It is mathematically represented as:

The significance of the loss tangent lies in its ability to quantify the efficiency of a dielectric material. A low loss tangent indicates that the material is a good insulator with minimal energy dissipation, which is critical for high-frequency applications, capacitors, and power transmission components. Conversely, a high loss tangent indicates significant energy loss, which can lead to overheating and potential dielectric breakdown.