Re: jumping ring demo

[Larry Woolf <larry.woolf@GAT.COM>]

Stating "a soft alloy with silver or copper" indicates an alloy of at least
two elements, where one of the elements is silver or copper.  It does not
mean pure silver or pure copper. If an element contains a small amount of
impurities, it is generally not considered an alloy - it just has some
impurities

Silver tarnish due to the formation of silver sulfide, not silver oxide.

Your table indicates that pure gold is more resistive than commercial gold.
These names have little meaning in terms of impurity content.  Resistivity
is most affected by impurities that substitute at lattice sites, and is less
affected by interstitial impurities.  Resistivity is also sensitive
synthesis parameters such as heat treatment temperatures (grain size, defect
density) and phase purity.

Larry


Can anybody see a difference between the following two positions?

 "A soft alloy with silver or copper can be more conductive
than pure aluminum." (me)
...is not the same as
"Can you give an example of a AgCu alloy that (at room temperature) is
> softer [and or a better conductor]  than the pure state of the
dominant constituent?"   (you)

Anyway, backing away from debating games, here you go with some
conductivity numbers
(but see below for Terms & Cons):

Gilding metal        31 nano ohm.meter
Aluminum Alloy 1100  29
Aluminum alloy 7072  29
Aluminum 99.99%      27
Gold, pure           25
Gold commercial      23
Copper deoxidized    20
Copper, electrolytic 17
Silver, pure         16 nano ohm.meter


Though I don't specially believe it, there *is* an example
of John's 'touchstone' case in the list above. Can you see it?

There is another comparison that I find much more interesting.
The conductivity of aluminum alloy 7072 is comparable to Aluminum
alloy 1100.
 The former has quite a dollup of zinc - the latter is
relatively pure. Wonder what's going on here?
brian whatcott