Inductance and Self-Resonance

Depending on the construction, an alternating current in the capacitor winding creates a more or less distinctive magnetic field which can be measured as inductance L (see equivalent circuit diagram).

The self-inductance L of modern capacitors - reduced by structural measures (e.g. contact over the end surfaces) - is approximately 10 nH. It is therefore not greater than the inductance of a wire, which is as long as the capacitor leads plus the lead spacing.

L and C form a series oscillating circuit; at a frequency of

the capacitor is in self-resonance and has the lowest impedance, which only consists of r (ESR equivalent series resistance).