stranded vs. single conductor resistance

Discussion in 'General Electronics Chat' started by TBayBoy, Jun 14, 2011.

  1. TBayBoy

    Thread Starter Member

    May 25, 2011
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    I've been looking at charts for resistance of copper wire, in general, I've been seeing stranded wire has less resistance than single conductor wire. This seems to go against my understanding.

    Is it solely due to the stranding increasing the circular mil. area, or some skin effect, or some other think I'm not getting.

    thanks.
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    Skin effect. Since like polarities repel each other, most of the current flows on the conductor surface.
     
  3. TBayBoy

    Thread Starter Member

    May 25, 2011
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    So with more conductor surface, there is less skin effect? So with resistance of 22 awg single strand is more than 20 awg not specifically because the wire is thicker and more free electrons, but more surface area.
     
  4. tom66

    Senior Member

    May 9, 2009
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    But wouldn't the skin effect only matter for AC?
     
  5. KJ6EAD

    Senior Member

    Apr 30, 2011
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    I seem to remember some other effects playing a role even in DC such as eddy currents and interstrand capacitance which may affect resistance.
     
  6. TBayBoy

    Thread Starter Member

    May 25, 2011
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    Good question
     
  7. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Skin effect is basically only accounted for with for AC currents (higher frequency the closer to the surface)
     
    Last edited: Jun 14, 2011
  8. wmodavis

    Well-Known Member

    Oct 23, 2010
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    Skin effect does not affect DC resistance of the wire. It does affect the AC impedance of the wire.
     
  9. TBayBoy

    Thread Starter Member

    May 25, 2011
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    OK, so we seem to be back to the original question, why does a single conductor wire have more resistance than the same sized multi strand wire?.
     
  10. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    The cross-sectional area, and hence the resistance, of any particular AWG should be identical between stranded and solid wire.
    Show us a link that says otherwise, and we'll look into it.
     
    #12 likes this.
  11. beenthere

    Retired Moderator

    Apr 20, 2004
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    TBayBoy likes this.
  12. TBayBoy

    Thread Starter Member

    May 25, 2011
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  13. Ron H

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    Apr 14, 2005
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    Your second link has this to say:
    Here is my interpretation of the lay factor:
    Each strand of twisted wire is in the shape of a helix. If you took a length of stranded wire, then unwound all the strands and straightened them out, each would be longer than its length when twisted, and therefore the resistance will be greater than that of an equal length of solid wire of the same gauge.
     
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  14. TBayBoy

    Thread Starter Member

    May 25, 2011
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    Thanks, I totally missed that... OK, no more drinking while reading electrical sites :)
     
  15. Ron H

    AAC Fanatic!

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    Snort! (snort again, to make the message length acceptable to the bean, er, letter counters).:D
     
  16. ForThePeople

    New Member

    Oct 26, 2014
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    I know this is an old thread but I figure I would give an answer that I think will clear up things up for a lot of people because it is one of the first links if you google "solid vs stranded wire resistance"

    Strand wire and solid wire of the same gauge are NOT the same diameter. The diameter of the same gauge strand wire is larger so that it has the same equivalent cross section area of metal as a solid wire. (this depends on the number of strands.) I think this is what confuses most people.

    I am unsure why you see less resistance even with the same cross section area, which its how I ended up here.

    source:
    http://en.wikipedia.org/wiki/American_wire_gauge
    read the first few sentences under "Tables of AWG wire sizes"

    http://en.wikipedia.org/wiki/Wire#Stranded_wire
    read the second paragraph under (forms or wire -> stranded wire)


     
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  17. MrChips

    Moderator

    Oct 2, 2009
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    You have to read the wikipedia article carefully (second link):

    Stranded wire of same diameter will have more resistance.
    Stranded wire with same cross-sectional area will have larger diameter and is given the same gauge.


    At high frequencies, the skin effect comes into play. The wire with greater surface area will perform better.
     
  18. baconc

    New Member

    Sep 1, 2015
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    Reading the above information, I have one important question.

    On copper braid screened cables, does the lay length of the braid affect the DC Resistance of the screen?

    I ask this question as I am informed by a far eastern manufacturer that shorter braid lays make the resistance deteriorate due to the distance the signal has to travel along the cable to reach it's end point.

    My opinion was always the shorter the braid lay, the better the resistance as you have more copper within the product.
     
    bwilliams60 likes this.
  19. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
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    try this on for size. Take a look here: http://www.seas.gwu.edu/~ecelabs/appnotes/PDF/techdat/swc.pdf

    Lok at 18 AWG wire. There are MULTIPLE ways of making 18 AWG wire. It consists of a number of strands of a lesser guage wire. None can have the identical circular area of 18 AWG solid wire, You can see it in the table.

    I used low stranding to be flexible, but positionable when I wired panels.

    Skin effect: Ac voltages only. In high power RF amplifiers, you will see wires as silver plated copper tubing. Silver has lower resistivity than copper.
     
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