Explain the terms dielectric constant and dielectric loss.

Dielectric Constant or Permittivity: all insulating materials possess an electrical capacitance. The capacitance of unit based upon dimensions and type of dielectric placed among the capacitor plates. The capacitance of a parallel plate capacitor may be computed from the formula C =∈ A/t, here ∈ is the permittivity of the material in F/m, A = Area of the plates and t = thickness of dielectric. And ε = C / C₀, here C is the capacity in presence of dielectric and C_o is the capacity in air or vacuum or in absence of dielectric.

Therefore permittivity ∈ of a material is a measurement of capability of it to form an electrical capacitance of the insulating material, the dimensions of the capacitor being taken equivalent. Dielectric constant or permittivity is not a constant although varies with temperature and frequency.

Dielectric loss angle:  While an insulating material is subjected to alternating voltage, several of the electric energy are absorbed through the insulation and are dissipated as heat. Energy absorbed through the material in unit time is termed as dielectric loss. A perfect dielectric has a current that leads the voltage by 900, although the practical dielectric material has a current that leads the voltage by less than 900. The dielectric phase angle is θ and δ = 900 - θ is the dielectric loss angle.

Also I is the phasor sum of I_d and I_c , here I_c is the conduction current that is in phase with applied voltage and I_d is the displacement current that is in quadrature phase along with applied voltage.