skin effect origin

Hi,

I know wat skin effect is and its implications..

Explian me how and y it occurs using e and m feild explanations.

regards

Hi, Resistance: I think you can look at the standard EM theory on plane wave incident into a metallic plane. You can solve the field inside the metallic plane. You will see the E and H field will be decaying exponentially when you are going into the metallic structure. Since J = sigma*E. It means that most of J is concentraing on the surface of the metallic plane. The concentration is more severe at higher frequency and it will cause more loss because the current is passing through an equivalently narrower cross-section. That is the so-called skin effect. As I mentioned, its implication is that there will be more loss at high frequency because the current is more concentrated. Regards.

The consequence of the skin effect is that the AC resistance will be higher than the DC resistance since the current is flowing through a smaller cross-sectional area

where

is resistivity,

is length and

is cross-sectional area.

take a look at the attached picture. Refer to the following page for more information about the web page for numerical values for cables. Do a google search and you will find lots of numerical information.

More on the ``skin effect"' : REACTANCE AND IMPEDANCE -- INDUCTIVE

Hope you find the information helpful.

Best regards,
v_c

Hi

When a conductor conducts current it establish a magnetic field, when this is changing as in AC systems, it induces small circular currents in the center of its conductor, which oppose the original current. These small current are called "eddy currents" and they generate there own magnetig field. This can deteriorate the fields ability to efficiently change direction which it often does in RF systems. They also dissipate energy in the form of heat.

But it is the eddy currents which decrease the current density in the center of the conductor and this leads to the increasing AC resistance.

Regards

hi tyassin,

Thanks a lot i think this was wat i was in the look out for..

Could we say due to lenz's law the eddy currents could be generated.. And how frequency influenves this feild formation. jus explain that too . I know inc in freq makes current flow more at the surface..

Y this is a phenomena only in conductors ??

regards..

I Guess J = sigma*E works for DC & AC so why skin depth appears only with AC??

hi,

u can look in feynman lectures in physics (vol. 1 and 2) by r.p.feynman for detailed physical origin of skin depth. another good book is elements of elecromagnetics by sadiku.

with regards
abhi

I Guess J = sigma*E works for DC & AC so why skin depth appears only with AC??