the model of electric flux in solids

dkastz

hi there!

I have a bit stupid question:

Imagine a solid metal cylinder. We put a . Explain to me please the exact model of the direct current electric flux of the particles. Is there a "skin effect" when a direct current is in action ?

yungman

You did not finish the sentence.

Is Direct Current means constant non varying current? If so, there is no skin effect to talk about, skin effect only happen with varying current and rather high frequency( no as high as people think!!).

There is no electric field inside a good conductor like metal if you assume it's a perfect conductor. Any electric field developed inside the metal WILL cause the electrons to move in opposite direction to neutralize the field. That's the reason there is no electric field in a perfect conductor.

In real life, there is a very very ( very!!) small electric field if you drive a current through as it's not a perfect conductor, a little voltage developed across the metal due to the resistance.

dkastz

grr i just saw that i missed the sentence!!!

Yes. you`re right - Direct Current means constant non varying current. I am wondering what happens inside the cylinder - where do electrons pass - all over the cross section or just at the surface. For the example the two points of current are the centers of the circular faces of the cylinder. What happens if i vary the diameter of the cylinder ?

yungman

If it is direct non varying current, the current density in the middle is the same as close to the surface. It is all over the cross section of the cylinder. Skin effect only applies to varying current.

http://en.wikipedia.org/wiki/Skin_effect

dkastz

deos this mean that in direct, non varying current, the conductivity/resistance is equal on the surface and in any point in the cross section (in case of perfect homogenic metal structure) ?