Material Effect On Skin Depth
In a good conductor, skin depth varies as the inverse square root of the conductivity. This means that better conductors have a reduced skin depth. The overall resistance of the better conductor remains lower even with the reduced skin depth. However the better conductor will show a higher ratio between its AC and DC resistance, when compared with a conductor of higher resistivity. For example, at 60 Hz, a 2000 MCM (1000 square millimetre) copper conductor has 23% more resistance than it does at DC. The same size conductor in aluminum has only 10% more resistance with 60 Hz AC than it does with DC.
Skin depth also varies as the inverse square root of the permeability of the conductor. In the case of iron, its conductivity is about 1/7 that of copper. However being ferromagnetic its permeability is about 10,000 times greater. This reduces the skin depth for iron to about 1/38 that of copper, about 220 micrometres at 60 Hz. Iron wire is thus useless for A.C. power lines. The skin effect also reduces the effective thickness of laminations in power transformers, increasing their losses.
Iron rods work well for direct-current (DC) welding but it is impossible to use them at frequencies much higher than 60 Hz. At a few kilohertz, the welding rod will glow red hot as current flows through the greatly increased A.C. resistance resulting from the skin effect, with relatively little power remaining for the arc itself. Only non-magnetic rods can be used for high-frequency welding.
Read more about this topic: Skin Effect
Famous quotes containing the words material, effect, skin and/or depth:
“True love ennobles and dignifies the material labors of life; and homely services rendered for love’s sake have in them a poetry that is immortal.”
—Harriet Beecher Stowe (1811–1896)
“The second [of Zeno’s arguments about motion] is the one called “Achilles.” This is to the effect that the slowest as it runs will never be caught by the quickest. For the pursuer must first reach the point from which the pursued departed, so that the slower must always be some distance in front.”
—Zeno Of Elea (c. 490–430 B.C.)
“my soul lingers over the skin of you
and I wonder if I’m ruining all we had,
and had not,
by making this break,
this torn wedding ring,
this wrenched life....”
—Anne Sexton (1928–1974)
“People who comprehend a thing in all its depth seldom remain true to it forever. For they have brought its very depth to light: and there is always so much nastiness to see there.”
—Friedrich Nietzsche (1844–1900)