In article . com, wrote:

Doug Miller wrote:
In article .com
, wrote:

You, however, seem to be unclear on the concept of skin depth.

Skin depth is a measure of the depth to which the electric field
penetrates the material. It is not, as you seem to believe, the
depth at which the current flows.

Speaking of unclear on the concept... an electric field is simply a field in
which work is done on an electric charge -- IOW, where current flows.

In a force field the potential to do work is present, whether work
is actually being done or not. Surely you'll agree that the electric
field extends beyond the wire into the surrounding air where no
current flows.

Yeah, I'll go along with that.

You do not need current to have an electric field. Light is
an example. The skin depth for light is real small.



IOW, you're wrong.

You might want to grab yourself a high school physics text and [re]acquaint

Wikipedia has good articles on the subject.

yourself with a few concepts before you so glibly assure CW that he's
mistaken. First, it's *static* charge that resides on the surface of a
conductor, *not* electric current. Second, the cloud of free electrons in a
metal extends throughout it, rather than being confined to the surface.

OK, you got me there.

I wasn't familiar with the relationship between skin depth and
current density. The current density at the center of #12 wire
is almost 90% of that at the surface, right?

I haven't run the numbers, but that sounds about right, maybe on the low side,
even.
[snip]
How about closing an AC circuit through a capacitor?
Would you agree that the AC 'passes' through the capacitor
even though the electrons do not?

In a sense, anyway -- but I think we're splitting hairs. Certainly if you
apply an alternating current to one side of a capacitor, you get an
alternating current out of the other side too.

BTW, other than the description at the top of the page,
I don't see any difference between NEC 310-19 and
NEC 310-18 he
http://www.houwire.com/products/tech...cle310_18.html
http://www.houwire.com/products/tech...cle310_19.html

Are those pages correct?

I didn't check every entry, but the first one appears to be correct. The
second one is definitely *not* correct: they have erroneously reproduced
310.18 under the heading of 310.19. The two tables are in fact substantially
different.


--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.