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Use.Netuser.de 02-08-2004 02:06 PM

Electrical Conductance
 
Hi Group

What defines a good conductor of electricity and why?

As I understand it from a search silver appears to be one of the best
conductors followed by copper, aluminium and gold at room temperature. I am
particularly interested in these materials as they are commonly used for
standard applications.

I've seen a move from copper to aluminium in high ampage DC applications and
been told that the cost of Aluminium is less than copper and the relative
difference in conductivity is not so important in such applications when
compared the product costs.

I also know that gold is commonly used in PCB fabrication etc and although it
is less conductive than the other materials above it's used because it does
not tarnish readily (oxidise) in air thus is ideal for such things as
connectors and PCB tracks prior to flow soldering.

Can we define a good conductor as one which can be produced with fewer
impurities thus less resistance or is it related to free electrons .... any
ideas!?

TIA



°Mike° 02-08-2004 02:56 PM

Re: Electrical Conductance
 
On Sun, 8 Feb 2004 14:06:33 -0000, in
<c05g95$12nf2k$1@ID-151068.news.uni-berlin.de>
Use.Netuser.de scrawled:

>Hi Group
>
>What defines a good conductor of electricity and why?


Homework?

<snip>

>I also know that gold is commonly used in PCB fabrication etc and although it
>is less conductive than the other materials above it's used because it does
>not tarnish readily (oxidise) in air


Gold (pure) is inert; it is unaffected by most reagents -- it's
the impurities that tarnish.

<snip>

--
Basic computer maintenance
http://uk.geocities.com/personel44/maintenance.html

philo 02-08-2004 03:08 PM

Re: Electrical Conductance
 

"Use.Netuser.de" <NoMilkTodayImOnHoliday@hotmail.com> wrote in message
news:c05g95$12nf2k$1@ID-151068.news.uni-berlin.de...
> Hi Group
>
> What defines a good conductor of electricity and why?
>
> As I understand it from a search silver appears to be one of the best
> conductors followed by copper, aluminium and gold at room temperature. I

am
> particularly interested in these materials as they are commonly used for
> standard applications.
>
> I've seen a move from copper to aluminium in high ampage DC applications

and
> been told that the cost of Aluminium is less than copper and the relative
> difference in conductivity is not so important in such applications when
> compared the product costs.
>
> I also know that gold is commonly used in PCB fabrication etc and although

it
> is less conductive than the other materials above it's used because it

does
> not tarnish readily (oxidise) in air thus is ideal for such things as
> connectors and PCB tracks prior to flow soldering.
>
> Can we define a good conductor as one which can be produced with fewer
> impurities thus less resistance or is it related to free electrons ....

any
> ideas!?
>
> TIA
>
>

Although aluminum is a good conductor...it is very much subject
to degradation. If you do not have an extremely good connection
it will tarnish and develop heat.

For a very brief period of time it was legal to use in house wiring...but
was made illegal due to fires being started. Also, with copper for example
you may flex it quite a bit before it breaks...aluminum is very brittle.

As far as wiring goes...copper is so close to silver as far as conductivity
that copper is the logical material to use...due to cost...

However when it comes to the use of connectors...if copper gets tarnished
it becomes a poor conductor...That's why gold is used in critical
applications.

Silver is also a good alternative for making electrical connections as it is
not only the best conductor...but silver-oxide is still a good conductor
unlike copper-oxide.



Use.Netuser.de 02-08-2004 03:11 PM

Re: Electrical Conductance
 
"°Mike°" <ZHNTPDWBLECA@fcnzzbgry.pbz> wrote
: Use.Netuser.de scrawled:

: >What defines a good conductor of electricity and why?
: Homework?

It was a question raised recent amongst a group of collegues and nobody could
answer it!? And we are all experienced engineers and one guy has a PhD in
Chemistry ...

Anyway the answers were "free electrons in the outer layer" and "purity of the
conductive material (metal)".
Finally after an exhaustive search the answer is

Valence Electrons:
The outer shell of an atom is known as the valence shell. Any electrons
located in the outer shell of an atom are known as valence electrons. The
valence shell of an atom cannot hold more than eight electrons. It is the
valence electrons that are primary concern in the study of electricity,
because it is these that explain much of electrical theory. A conductor for
instance, is generally made from a material that contains one or two valence
electrons. Atoms with one or two valence electrons are unstable and can be
made to give up these electrons with little effort. Conductors are materials
that permit electrons to flow through them easily. When an atom has only one
or two valence electrons, these electrons are loosely held by the atom and are
easily given up for the current flow. Silver, copper, gold, and aluminum all
contain one valence electron and are excellent conductors of electricity.
Silver is the best natural conductor of electricity, followed by copper, gold,
and aluminum.

: <snip>
:
: >I also know that gold is commonly used in PCB fabrication etc and although
it
: >is less conductive than the other materials above it's used because it does
: >not tarnish readily (oxidise) in air
:
: Gold (pure) is inert; it is unaffected by most reagents -- it's
: the impurities that tarnish.
: <snip>

Interesting. Thanks




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