Re: [tlug] Gold Fever

[Jim <jep200404@example.com>]

"Lyle (Hiroshi) Saxon" <ronfaxon@example.com> wrote:

> But if silver - a cheaper material than gold - is bypassed for gold for 
> contacts, then I think oxidation is an issue?  

Oxidation of silver _can_ be an issue. 
Even when it is, there are plenty of solutions, 
some including gold plating, many not including gold plating. 

> So maybe it's this - for 
> internal conductivity (according to the above chart), silver is better, 

Silver is not merely better, 
it is the _best_ conductor at temperatures that we experience. 
(I.e., never mind Pons and Fleischmann)

> but gold's stronger resistance to oxidation makes it a better conductor 
> when external physical contact is the issue?

Gold is never a better conductor than silver. 

Gold plating of silver or copper is a compromise between the 
poorer conductivity of gold and the even poorer conductivity 
of oxides. The compromise favors gold when you don't really 
need super low joint resistance, but just need to avoid bad 
contacts for casual connections (like with RCA patch cords 
for audio/video equipment). 

If you really care about having a low resistance connection, 
you will not accept the compromise. You will rely on other 
solutions. 

If you have a contact that is made and broken under current 
(especially with inductive loads), you will _not_ choose gold 
plating, you might choose bare silver buttons, tarnish be darned. 

If you care about incidental thermocouples, 
you will not use plating of any kind. 

Back to silver tarnish, from the wiki page: 

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

   ... silver's superior conductivity, even when tarnished. 

   Silver oxide is used as a positive electrode (cathode) in watch batteries.

[electrodes are conductive]

The most powerful effect of gold is to tarnish the minds of people 
with the thought that because it is expensive, that it must be 
better.