Parasitic Inductance

Question

when we say that in a wire there is a parasitic inductance, what is its cause? Is it the skin effect of the wire, the magnetic flux (generated by the current) through the surface of the total circuit in which the wire is inserted, or others?

I was told it is the skin effect of the conductor, but I was thinking that the dependence of the impedance is not linear so it should be wrong to consider this phenomenon as an inductance.

The cause is physics. Any current, anywhere, has inductance, no matter what. The skin effect is a different thing entirely. (though related in that both are electromagnetic phenomena) — Hearth, Mar 15 '19 at 20:02
It's similar to how all mass has inertia. I think this is similar to asking "why does mass have inertia"? — DKNguyen, Mar 15 '19 at 20:28
@Toor That doesn't make it a bad question though. It's quite a deep one, in fact. — Hearth, Mar 15 '19 at 20:37
I never said it was a bad question, but I do think that believing you can break it down into discrete high-level electrical principles is the wrong way to go about it, considering that it's nearly impossible to to do the equivalent with the mechanical analog. The difference is that no one approaches inertia the same way because we are all born with some mechanical intuition so everyone has the innate understanding that you can't approach inertia that way). — DKNguyen, Mar 15 '19 at 20:46
Both boil down to "nothing happens in instantly". I also think that it helps to consider what would happen if there was no parasitic inductance. It would mean there would be no inductance anywhere at all since inductors just ramp up the same parasitic effect. It's like considering an material with no weaknesses (indestructible). If it existed, then how did it even form at all since it could never be broken down to begin with? That tends to happen with idealities. — DKNguyen, Mar 15 '19 at 20:53
Why is the relativistic force between fixed charges and the moving charges at RIGHT ANGLES to the "magnetic field"? — analogsystemsrf, Mar 16 '19 at 03:58
It's not due to the skin effect, however, the skin effect is due to the same reason that a wire stores energy in the space around it. The number we put on the proportionality between stored energy and current squared, is given the name inductance. — Neil_UK, Mar 16 '19 at 06:45

score 3 · Accepted Answer · answered Mar 15 '19 at 20:08

Generally, an inductance (parasitic or otherwise) indicates energy being stored in (and recovered from) the magnetic field.

Any current through a wire produces a magnetic field around the wire. But that magnetic field stores energy. Therefore you can't produce the current instantaneously (unless you can deliver infinite power). And if you want to shut the current off, you need to absorb that energy somewhere else.

With a bit more math to put numbers to things (how much current produces how much magnetic field, storing how much energy) you have your inductance.

Parasitic Inductance

1 Answers1