Talk:Skin depth

Why is this listed as a geology stub when the majority of the information (even before my edit) is based on the electrodynamic definition of skin depth? I'm sure there are perfectly valid uses of the idea of skin depth in geology, but they don't appear here.

Maybe this article should be moved?

Skin depth is just a measure of how far into a material an EM wave can go. This is based on electromagnetic principles. However, it has practical applications in areas such as oceanography and geology, where low-frequency EM waves can be sent through water or rock. --Yuje 09:59, 22 June 2006 (UTC)

I understand that skin depth may be applied to almost any situation where energy is being transferred by a wave motion, however it seems like this entire article is based on the electrodynamic definition, with only the slightest of nods towards its use in geology. Since the majority of its content is based on electrodynamics, perhaps it should be moved to a more suitable place. Either that, or rewritten to have the majority of its content refer to geology and not physics. sdmolloy 20:02 27 June 2006 (UTC)

The statement of 50x greater skin depth in Al over Fe in this page is not born out by the numbers. They show 5 ?? kroberts 11/20/06

All the above issues have been addressed. However, the article is recognised as having major flaws in content, accuracy and presentation. These will be addressed in due course. StuFifeScotland 21:56, 21 January 2007 (UTC)

Hi, I'm a student trying to learn about skin depth. From the information on the page, it seems like a skin depth is an AC phenomenon. However, based at the calculation at the bottom of the page, skin depth is inversely relational to the square root of the frequency, making the skin depth infinite in DC. Does this mean that the higher the skin depth, the more constant the charge in the wire?

The skin depth is indeed "infinite" at DC - in other words, current runs along the entire depth of the wire. Nickwithers 11:12, 13 March 2007 (UTC)

Indeed: the skin effect strengthens as the frequency goes up, which is equivalent to saying the skin depth gets smaller (and will eventually, at high enough frequencies, be less than the radius of the wire). When time allows, I still intend to make major improvements to this article, to make clear what's going on inside the conductor. Meanwhile, take a look at the Eddy Currents article, because eddy currents within the wire are implicated in the skin effect. The higher the AC frequency, the faster the magnetic field in and around the wire strengthens, weakens and reverses. This rapidly changing magnetic field induces strong eddies in the flow of electrons, and these induce magnetic fields of their own. If the resistance of the material is low, then the electrons retain more of their kinetic energy as they swirl through the lattice, so they produce strong induced fields. That's why the skin effect is most pronounced in situations where: a) the AC frequency is high and b) the resistivity is low. StuFifeScotland 14:48, 27 March 2007 (UTC)

One question about frequency dependency...

"Hence, the higher magnetic permeability of iron more than compensates for the lower resistivity of aluminium and the skin depth in iron is therefore 5 times smaller. This will be true whatever the frequency, assuming the material properties are not themselves frequency-dependent."

Is the permeability of iron really independent from frequency? eivindtoreid 08:24, 01 May 2009 (UTC)

Iron permeability varies quite a bit especially above 1 MHz. It typically has a low frequency permeability of 10,000 rather than 90. The section quoting this needs to be fixed.Trojancowboy (talk) 02:18, 3 June 2009 (UTC)

Alpha and Beta

According to Griffiths... We have the +-1 reversed I think. --Falcorian ^(talk) 00:31, 30 January 2008 (UTC)

"How does the plot of current density variation for a alternating current carrying conductor along diameter look like. Which equation governs it as a function of frequency, permeability, and resistivity? delta"