Tan of Dielectric Loss Angle

n In a ideal condenser of geometric capacitance C_o, in which the polarization is instantaneous, the charging current ${\rm{E}}\omega \varepsilon^\prime$C_o is 90^o out of phase with the alternating potential. In a condenser in which absorptive polarization occurs, the current also has component ${\rm{E}}\omega \varepsilon ^{\prime\prime}$ C_o in phase with the potential and determined by Ohm’s law. This ohmic or loss current, which measures the absorption, is due to the dissipation of part of the energy of the field as heat. In vector notation, the total current is the sum of the charging current and the loss current. The angle δ between the vector for the amplitude of the total current and that for the amplitude of the charging current is the loss angle, and the tangent of this angle is the loss tangent of dielectric loss angle:

$$\tan \delta = {{{\rm loss \ current}} \over {{\rm charging\ current}}} = {{\varepsilon ^{\prime\prime}} \over {\varepsilon^\prime}}$$

where ε′ is the...