Surface coating and electrical conductance

[nukie]

Hello all, I have a question. Google gives me answer my small brain could not understand, so I need help.

I read that AC current travels on the surface of a conductor. So given two different conductor made out of different material, say brass and nickel. Coat it with gold. Now both have same surface resistance, so what about electrons flow rate ? Assuming both conductors are equal in physical dimension.

[Zero999]

It's only true at high frequencies which is why silver plating high frequency conductors is useful in reducing their resistance.

[vk6zgo]

A warning on silver plating.
Normal plating as used for sporting trophies,etc has additives to increase the brightness &
durability.
These increase the RF resistance to a higher figure than plain copper.
Special plating is used for RF conductors.

VK6ZGO

[Time]

You should read about the skin effect.  Thats the phenomenon you are interested in.

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

All AC currents know this effect it just becomes more apparent from an engineering stand point in higher frequencies.  I believe the skin depth for 60 Hz in copper is about a cm or something.

[nukie]

Yes skin effect is what prompted my question.

I was looking at my meter probes and some banana jacks and it got me thinking why some are gold plated while most are chrome/nickel plated. I prefer standard plating, gold would be too soft and wear out too quickly especially around the contact areas.

Now I also understand why those high frequency wifi antenna jacks are mostly gold plated. Thanks guys!

[the_raptor]

Gold oxidises less then chrome/nickel AFAIK. It might wear off from frequent disconnection and reconnection but it won't easily build up an oxide layer thick enough to impede electrical current.

In PC repair I have seen non-gold plated connections fail after a handful of years and require cleaning.

[Zero999]

Now I also understand why those high frequency wifi antenna jacks are mostly gold plated. Thanks guys!

Then you've completely misunderstood.

Connector are gold plated to improve corrosion resistance and has nothing to do with the skin effect. Copper is a much better electrical conductor than gold and is much cheaper too. Gold plating reduces the contact resistance because an insulating oxide doesn't form on it.

http://en.wikipedia.org/wiki/Electrical_conductivity#Resistivity_of_various_material