On 11 Feb 2004 08:11:15 -0800, (Svante)
wrote:

CJT wrote in message ...
Wessel Dirksen wrote:
"CJT" wrote in message
...

snip
Nobody commented on my observation earlier in the thread that the
Earth's magnetic field could bias the hysteresis curve in certain
orientations. g


I personally thought you were making a joke.

I was. But that sort of thing is similar to other audiophile
legends. Skin effect comes to mind; nobody denies its existence,
but to claim an audible effect exceeds credibility.


Hmm. Pardon me if I am drifting off topic here, but I and a collegue
of mine recently noticed a quite noticeable deviance from the Z=wL in
the impedance of inductors in the HF range. These inductors were made
of standard ~0.3mm (I'll have to check this) wires and no iron core
(for loudspeaker crossovers). Any explanation to this, apart from
skin?
http://www.tolvan.com/coil.gif
Note that I don't claim big *audible* effects from this in most
applications, though.

---
Probably because Z does _not_ equal wL, inductive reactance (Xl) does.

That is,

Xl = wL = 2pi*f*L

In a series circuit containing resistance, inductance, and capacitance,
the impedance (Z) of the circuit will be equal to the square root of the
sums of the squares of the resistance and the square of the difference
between the inductive and capacitive reactance. That is,

Z = sqrt (R² + (Xl - Xc)²)

Of course, in a circuit containing only inductance, the inductive
reactance and impedance will be equal. However, such a scenario is
impossible and the effects of capacitance and resistance must always be
considered if accuracy is important.

Looking at just the inductor, since there is a voltage difference
between turns and the turns are dielectrically isolated from each other,
that gives rise to an inherent capacitance and since there is resistance
in the wire used to wind the inductor, that's also part of the inductor
and can't be separated from it. There are winding techniques used to
minimize the capacitance (which appears to be in _parallel_ with the
inductance) but in the case of coils wound for loudspeaker crossovers,
I'd seriously doubt whether the slightest consideration was given to
them. I suspect the resistance of the wire is what's causing the
deviation from "ideal" inductance, and I also suspect that skin effect
has _nothing_ to do with it since that's an effect which starts to
become significant at radio frequencies.

--
John Fields