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# my question is about big capacitor and it's parasitic inductance.

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#### xljin2006

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we know big capacitor has two big plates of two electrodes. it's said capacitor has parasitic inductance because the plates are curled tight. my question is: how this can make parasitic inductance?how the electrons flow on the plate while the capacitor is changing or discharging?and the next question is more important: why the parasitic inductance is seriesly connected to the capacitor?

Solution
A discussion of L in parallel plates :

Regards, Dana.

A discussion of L in parallel plates :

Regards, Dana.

When the plates of a capacitor are curled tightly, it creates a coil-like structure that can introduce parasitic inductance into the capacitor. This is because any current flowing through the capacitor must also flow through the coiled structure of the plates, which causes a magnetic field to be generated around the plates. This magnetic field, in turn, induces a voltage across the plates that opposes the flow of current, just like in an inductor.

The inductance introduced by the coiled structure of...
so why they are series and not parallel?
Here is a plot from a VNA. It is a machine that measures the impedance of the capacitor at many different frequencies. On the left side is low frequency and the impedance is very high. We can see at 1mhz = 1 ohm. There is a resonant point at 17mhz and then the capacitor goes inductive. This is a very common graph for the capacitors that I have studied.

so why they are series and not parallel?
As demonstrated by ronsimpson, a capacitor exhibits a series resonance with its parasitic series inductance.

Also be aware that inductors have parasitic capacitance, which is effectively in parallel with the inductance.
So that an inductor exhibits a parallel resonance with its parasitic parallel capacitance.

JimB

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