# Electrical conductivity of metals



## JimmyM (Jan 31, 2007)

I'd read in a lot of places that lights, etc are built with brass instead of aluminum/aluminium for better electrical conductivity.

However, real data proves otherwise.

In order of electrical conductivity (relative to copper)
Material IACS % Conductivity 
Silver 105% 
Copper 100% 
Gold 70% 
Aluminum/Aluminium 61% 
Nickel 22 % 
Zinc 27% 
Brass 28% 
Iron 17% 
Tin 15% 
Phosphor Bronze 15% 
Lead 7% 
Nickel Alum. Bronze 7% 
Steel 3 to 15%

That's right, Gold is only 70% as electrically conductive as copper.
Brass is only slightly more than 25% as conductive as copper.
There are other factors, not the least of which, are solderability and corrosion resistance. But for electrical conductivity, It's tough to beat copper.


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## viorel00 (Jan 31, 2007)

this reminds me, in my grandma's house, very old, there was a circuit that had both Aluminium (yes, this is the right spelling) and Copper wires. What happened, you flipped the switch, and the light bulb turned on about 2-3 minutes later! Then if you quickly turned it OFF and back ON all was normal. But if you left it OFF and came back the next day, you had to wait 2-3 minutes. I was told there were a poor contact somewhere between Al and Cu, but no one had the time to troubleshoot it. Now the house is unoccupied, and 7000 miles form here, so...


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## JimmyM (Feb 1, 2007)

viorel00 said:


> this reminds me, in my grandma's house, very old, there was a circuit that had both Aluminium (yes, this is the right spelling) and Copper wires. What happened, you flipped the switch, and the light bulb turned on about 2-3 minutes later! Then if you quickly turned it OFF and back ON all was normal. But if you left it OFF and came back the next day, you had to wait 2-3 minutes. I was told there were a poor contact somewhere between Al and Cu, but no one had the time to troubleshoot it. Now the house is unoccupied, and 7000 miles form here, so...



When copper and aluminum (Spelling see below) are placed in contact with one another, galvanic corrosion can occur which creates resistance and thus heat, which can cause fires. There was a big problem with this in the states when houses were wired with aluminum instead of copper and the electrical properties of the connections at the switches and outlets was not taken into consideration. Corrosion-->heat-->fires. If metallurgy is taken into consideration, aluminum wiring is cost effective and safe.

See http://en.wikipedia.org/wiki/Aluminium#Spelling

I'll choose to spell it the way the person who named it settled on.

The earliest citation given in the Oxford English Dictionary for any word used as a name for this element is _alumium_, which Humphry Davy employed in 1808 for the metal he was trying to isolate electrolytically from the mineral _alumina_. The citation is from his journal _Philosophical Transactions_: "Had I been so fortunate as..to have procured the metallic substances I was in search of, I should have proposed for them the names of silicium, alumium, zirconium, and glucium." [14]

By 1812, Davy had settled on _aluminum,_ which, as other sources note, matches its Latin root. He wrote in the journal _Chemical Philosophy_: "As yet Aluminum has not been obtained in a perfectly free state."[15] But the same year, an anonymous contributor to the _Quarterly Review,_ a British political-literary journal, objected to _aluminum_ and proposed the name _aluminium_, "for so we shall take the liberty of writing the word, in preference to aluminum, which has a less classical sound." [16]

The _-ium_ suffix had the advantage of conforming to the precedent set in other newly discovered elements of the period: potassium, sodium, magnesium, calcium, and strontium (all of which Davy had isolated himself). Nevertheless, _-um_ spellings for elements were not unknown at the time, as for example platinum, known to Europeans since the 16th century, molybdenum, discovered in 1778, and tantalum, discovered in 1802.


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## Led_Blind (Feb 1, 2007)

Sorry but aluminium is aluminium  And Mooinites in Boston are not bombs

TIC intended


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## PhantomPhoton (Feb 1, 2007)

:huh2:
I thought brass lights were used instead of aluminum sometimes for better _heat_ conductivity.


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## digitor (Feb 1, 2007)

I think the reason that using brass results in better system conductivity is, that you can solder to brass, but you have to use a riveted (or similar) connection to aluminium. (solder/soder, aluminium/aluminum) A connection like this often results in high resistance problems over time.

Cheers


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## MrAl (Feb 1, 2007)

Hi there,

Just to note, brass has a fairly bad heat conductivity also, compared to copper
it is somewhere in the neighborhood of 1/3 as conductive, similar to it's relation
to the electrical conductivity. Aluminum is better than brass also similar to
it's electrical spec.
Steel pretty much bites too, and if you try making a soldering iron tip out of
steel (very durable) it has to be shorter in order to conduct the heat properly,
but if slightly longer it can be used to reduce heating power for use when
soldering smaller items.


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## DM51 (Feb 1, 2007)

Where does Titanium fit in that table? And what is the most conductive material there is? I assume some superconductor - but aren't the latest superconductors ceramic, only operating at very low temperatures?


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## JimmyM (Feb 1, 2007)

Led_Blind said:


> Sorry but aluminium is aluminium  And Mooinites in Boston are not bombs
> 
> TIC intended



Yeah. no kidding. Can you believe that BS? The plice actually had the nerve to charge them with building a hoax device. Mostly out of embarassment, I'm sure.


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## JimmyM (Feb 1, 2007)

DM51 said:


> Where does Titanium fit in that table? And what is the most conductive material there is? I assume some superconductor - but aren't the latest superconductors ceramic, only operating at very low temperatures?



Yeah, you're right. Zero resistance would be better. I believe a "high temperature" super conductor is oner that operates at liquid nitrogen temperatures.
Of the naturally occuring metals, I believe Silver is best though.


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## turbodog (Feb 1, 2007)

Silver has the best electrical conductivity and thermal as well.

But, it's got some cost issues.


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## IMSabbel (Feb 1, 2007)

In all metals, thermal and electrical conductivity are extremely related.
The reason for this is the rather low debeye temperature of the crystal latices. As a result, nearly all the thermal conductivity is provided by the electrons. And thus, materials that have highly mobile electrons (-> good electrical conductors) also are good for thermal transfer.
5 point for the one to know the name of the law that descripes above behaviour 

Btw: The _best_ thermal conductor BY FAR is diamond. More than twice as good as copper at room temperatur (here the very stiff crystal latice allows a broad range of phonons to carry energy). With diamond getting easier to create via vapour deposition, headspreaders for high energy semiconductors (i.e. laser diodes, high flux leds, high end processors) could be viable the next 5 years.


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## matrixshaman (Feb 1, 2007)

Wiedemann-Franz Law


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## DM51 (Feb 1, 2007)

matrixshaman said:


> Wiedemann-Franz Law


If you break it is that a felony or just a misdemeanor?


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## eluminator (Feb 1, 2007)

I don't think conductivity of the bulk metal is an issue here. But contact resistance is. Aluminum always has a coating of aluminum oxide and I'm guessing it is an insulator.

Brass contacts are good enough for many things, but they do oxidize which makes for high contact resistance.

Nickel plating is good and I believe most batteries have this. I don't know if you can plate aluminum. I've never seen it done.


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## matrixshaman (Feb 2, 2007)

IMSabbel said:


> In all metals, thermal and electrical conductivity are extremely related.
> The reason for this is the rather low debeye temperature of the crystal latices. As a result, nearly all the thermal conductivity is provided by the electrons. And thus, materials that have highly mobile electrons (-> good electrical conductors) also are good for thermal transfer.
> 5 point for the one to know the name of the law that descripes above behaviour


The answer is the Wiedemann-Franz Law - for DM51 - and for you that will be a misdemeanor :hahaha:


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## NewBie (Feb 3, 2007)

JimmyM said:


> I'd read in a lot of places that lights, etc are built with brass instead of aluminum for better electrical conductivity.
> 
> However, real data proves otherwise.
> 
> ...






DM51 said:


> Where does Titanium fit in that table? And what is the most conductive material there is? I assume some superconductor - but aren't the latest superconductors ceramic, only operating at very low temperatures?



For one of the common Ti alloys, Ti6Al4V:
0.000178 ohm-cm
http://www.matweb.com/search/SpecificMaterial.asp?bassnum=MTP641

For one of the Electronic grade Coppers:
0.00000169 to 0.00000173 ohm-cm
http://www.matweb.com/search/SpecificMaterial.asp?bassnum=MC102A

This would put Titanium at 1% of the electrical conductivity of copper, near the bottom of the list. As for the overall electrical conductivity in a light, one needs to consider the cross-section of the material that is present and the current that flows. It may not be a factor at all, depending on the design, such as wall thickness and contact area.

In order of electrical conductivity (relative to copper)
Material IACS % Conductivity 
Silver 105% 
Copper 100% 
Gold 70% 
Aluminum 61% 
Nickel 22 % 
Zinc 27% 
Brass 28% 
Iron 17% 
Tin 15% 
Phosphor Bronze 15% 
Lead 7% 
Nickel Alum. Bronze 7% 
Steel 3 to 15%
Titanium 1%


On a side note about Titanium

Thermal Conductivity-

Titanium:
6.7 W/m-K
http://www.matweb.com/search/SpecificMaterial.asp?bassnum=MTP641

Copper:
383 - 391 W/m-K
http://www.matweb.com/search/SpecificMaterial.asp?bassnum=MC102A


So the thermal conductivity of Titanium is also 57 times worse.


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## chris_m (Feb 3, 2007)

JimmyM said:


> See http://en.wikipedia.org/wiki/Aluminium#Spelling


"The International Union of Pure and Applied Chemistry (IUPAC) adopted _aluminium_ as the standard international name for the element in 1990, but three years later recognized _aluminum_ as an acceptable variant. Hence their periodic table includes both, but places aluminium first. IUPAC officially prefers the use of _aluminium_ in its internal publications, although several IUPAC publications use the spelling _aluminum_."

So we're right, but you're not totally wrong :touche:


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## JimmyM (Feb 3, 2007)

chris_m said:


> So we're right, but you're not totally wrong :touche:


Well researched. So, I was originally right. And now you're currently right.
I can live with that.
See my original post.


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## chris_m (Feb 3, 2007)

You gave me all the research materials yourself 

Anyway, we all know that the wiki is always right, and on that basis, I think the title of the article you referenced is quite telling


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