Copper conducts better than Gold?

Discussion in 'Physics' started by dor, Jan 6, 2016.

  1. dor

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    Last edited: Jan 6, 2016
  2. OBW0549

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  3. dor

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  4. Alec_t

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    Because gold doesn't oxidise.
     
  5. OBW0549

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    No. The electrical conductivity of metals is something that has been accurately known for well over a century.

    Unlike copper, gold doesn't tarnish. That makes it useful in electrical contacts, such as in connectors. Also, the lack of oxidation makes gold easy to solder. Hence, its widespread use in electronics.
     
  6. alfacliff

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    silver is the best conductor. copper is better than gold. gold is a "noble metal" and does not oxidise. copper and silver do oxidise, which will raise their restivity.
     
  7. KL7AJ

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  8. GopherT

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    For a given size of wire, true.

    However, is it really fair to say a wire that weighs 10% more than copper is a "better" conductor? And costs $490.00/kg while copper costs $4.65/kg.

    Going the other direction, is copper such a great conductor when an aluminum cable of half the mass can carry as much current? That means, for every $4.65 of copper, you only need $0.65 of aluminum.

    The resistivity x density product is the standard for mass conductivity (all other comments so far have related to the volumetric conductivity).

    It is understood that joining the aluminum to other aluminum cables can be an issue and has its own costs (otherwise aluminum PCBs would be the "gold" standard in the industry).

    My point is, "best" is not always best. It depends on the situation. Power lines where weight and cost are important, aluminum is a superior choice. In corrosive situations or where soldering is an issue, gold-plated copper is good. If abrasion is an issue, solid gold is best (if the application can support the price).

    Note that the three most conductive materials on a mass basis are the three most easily corroded materials - sodium, lithium and potassium (in order of resistance density product, "best" being sodium). Interestingly, in large volumes, sodium is roughly half the price of copper per kilogram. And, sodium can carry 3x the current for an equivalent mass. Therefore, a $4 cable of copper could be replaced with about $0.70 worth of sodium.

    Unfortunately, sodium melts at about 100 C - suddenly a liquid conductor!

    Sodium/potassium alloys exist as liquids at room temperature. Imagine Eddie currents in liquid metal? At room temperature?

    Also, materials that are good electrical conductors are also good thermal conductors. Now, imagine the heat sinks that could be made with these alloys - excellent thermal conductors to draw heat away from the source, but it can also be pumped. It can also withstand 800 C while developing a vapor pressure of only 1 ATM (if kept from water or oxygen).

    Good night!
     
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  9. KL7AJ

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    It's just REALLY hard to solder to sodium wires. :)
     
  10. GopherT

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    Just crimp.
     
  11. alfacliff

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    trying to say that just because a metal is cheaper makes it a better conductor is false. and for silver being heavier is what makes it a better conductor, conductors will be smaller to handle the same current as copper. if it were weight that makes conductors better, uranium would be a great conductor.
     
  12. boatsman

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    @GopherT
    You forgot to mention that sodium and potassium are so reactive in air that they are normaly stored covered in mineral oil.
     
  13. GopherT

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    Laboratory samples or small commercial quantities, yes, in mineral oil. Commercial quantities in truckloads or rail cars, are just kept in a closed containers. Melted, and pumped to the usage point. But yes, as I said above, "the most easily corroded metals."

    My point seemed to fly past you. I said above,
    There is no single definition of "Best". "Best" depends on the situation. ​
     
  14. alfacliff

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    best conductor of electricity is a standard.based on resistivity.and resistivity is based on standard size conductors. if you want to specify heat conduction, silver is best, if you want to specify resistance to corrosion, gold is better. if you want the most resistant to heat, tungsten is better, you said in the origional post, conduction.
     
  15. BR-549

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    How does graphene conduction fit in here.
     
  16. alfacliff

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    it fits when it gets published . but everything has to have standards for measurement. having the resistance of a ton of gold compared to an ounce of copper is invalid. when graphene gets to where they can fabricate it ito the standard for resistivity measurement..
     
  17. BR-549

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    ok, so your saying that until we manufacture graphene to where we can carry comparable currents, we can't really make a comparison. I guess that makes sense.
     
  18. alfacliff

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    no, I am saying that when graphene can be manufactured to the resistivity standards length and area so it can be measured, it will have just a guess as to its resistivity.
    how would you compare the resistivity of 1/2 inch of #32 copper to a foot of 1/2 inch thick silver? there have to be standards of measurements. going by the silly comparisons to compare resistivity is not scientific. resistivity standards are also standards of area and length of material to be measured. equal length and area of copper and gold when compared give copper the lower resistivity at the same tempratures
     
  19. BR-549

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    What do you think I meant by "comparable currents"? I wouldn't call 1/2 " of #32 copper and 1/2 foot of silver............comparable either. I was trying to say I understand your point.
     
  20. GopherT

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    I said that another method to compare, depending on needs, is to compare RESISTIVITY x DENSITY PRODUCT

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