The technical capacitor model presented in the introduction page on the capacitor models shows that the impedance real part of a technical capacitor
is due to the capacitor series resistance r_{s} and to the capacitor parallel resistance r_{p}.

The contribution due to r_{s} is important at high frequency
while the contribution due to r_{p} has a dominating effect essentially at low frequency,
in particular at the industrial frequency.

In r_{s} are collected the resistances of the conductors, connections, electrodes and electrolyte if necessary.
In r_{p} are collected the losses due to the dielectric polarisation, the dielectric resistance, the losses due to the
leakage current and the charges redistribution phenomena if necessary.
In a theoretical or mathematical capacitor, the power is purely reactive. There are no losses.

The losses are given by: P_{L} = r_{s}i^{2} + r_{p}IR^{2}.

In order to simplify the calculation, an "Equivalent Series Resistance" is used insteed of r_{s} and r_{p}. The theoretical
presentation is given in the link below.