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resistance of various metals

Discussion in 'Electronic Basics' started by Chris W, Feb 25, 2008.

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  1. Chris W

    Chris W Guest

    I have seen charts that show how the resistance of various metals
    compare. What I haven't seen is a way to make determine how much larger
    say a stainless steel rod would need to be to have the same resistance
    as a copper rod of some given diameter. For example if I had a 30 awg
    copper wire and a 1" dia Stainless steel rod, even though the copper is
    a better conductor, in this case the 1" dia stainless steel rod is going
    to have less resistance. Is there a rule of thumb, or chart that tells
    how much larger to make a conductor to have equivalent resistance to copper?


    --
    Chris W
    KE5GIX

    "Protect your digital freedom and privacy, eliminate DRM,
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  2. Phil Allison

    Phil Allison Guest

    "Chris W"

    ** Are you for real ????

    Got no idea that a wire's or rod's resistance is * inversely proportional *
    to its cross sectional area ?

    Ever figure out that two similar wires run in parallel have half the
    resistance of one ???




    ** A real dope -

    even by the most humble standards of ham operators.



    ........ Phil
     
  3. Al Forster

    Al Forster Guest

    "Chris W" wrote in message news:20vwj.5938$...
    No chart that I'm aware of, but not difficult to calculate. Find a
    table of resistivities for metals eg
    http://en.wikipedia.org/wiki/Electrical_resistivity#Table_of_resistivitiesand calculate fromResistance = (resistivity * length) / x-sectional area.Hope this helpsAl
     
  4. Chris

    Chris Guest

    Easy to calculate from the equation Al gave. Total resistance is the
    same, total length is the same, so if you have a material that's eight
    times the resistivity, by the equation it will have to have eight
    times the cross-sectional area. Simple algebra.

    Which means the resistivity chart the OP is looking at is actually the
    chart he needs -- if he has a calculator, he can divide the
    resistivity of stainless steel by the resistivity of copper, and that
    tells him how many times more cross-sectional area he needs.

    And a newbie alert if Chris is doing the calculations to determine
    resistance instead of just calculating ratios -- watch your terms.
    Charts for resistivity are frequently expressed for CM, circular
    mils. One circular mil is the area of a circle 1 mil in diameter.
    This is *not* 1 square mil -- you need to convert!

    http://en.wikipedia.org/wiki/Circular_mils

    Good luck with your studies.
    Chris
     
  5. #Table_of_resistivities

    You will have to look up or determine the resistivity of your specific
    stainless steel - there are a lot of different stainless steels.

    - Don Klipstein ()
     
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