Re: [Phys-L] aluminum resistivity

[John Denker <jsd@av8n.com>]

On 07/21/2014 09:22 AM, Folkerts, Timothy J wrote:
> The wires are almost certainly an alloy, so the resistivity will
> probably be noticeably larger than pure Al.  Apparently "1350-h19" is
> a common alloy for wires, 

Right.

Note that's still 99.5% Al.

> and you can find a resistivity of 28.2 uOhm-cm

Right.

That's about 6% more than the accepted value for ultra-pure Al.

That alloy is carefully designed to make a tradeoff between 
mechanical strength and conductivity.  This stands in contrast 
to alloys designed for mechanical strength alone, which have
really terrible conductivity.

Also:
  Although the conductivity of the commonly used conducting 
  alloy (1350) is only around 62% of annealed copper, it is 
  only one third the weight and can therefore conduct twice 
  as much electricity when compared with copper of the same 
  weight.
That's a quote from
  http://www.azom.com/article.aspx?ArticleID=2863

================

Note that for some applications, it pays to use cable with 
high-strength strands in the middle and high-conductivity
strands on the outside:
  http://www.sural.com/products/bare/acar.htm

================

We can do some fun physics with this:

Note that the resistivity of pure Al is due to scattering
by thermal phonons.

The resistivity of the alloy includes the aforementioned
thermal phonon scattering, plus a smallish amount of
impurity scattering.

The phonon contribution is linear in temperature at high
enough (non-cryogenic) temperatures.  So from winter to
summer you can see a 10% variation in this contribution.

So ... the temperature correction term is on the same order
of magnitude as the alloy correction term.