Does the NEC rate 14 gage stranded wire (with much more surface area than 14 awg solid wire, for more amperage? Nah. Not with pure copper wire. (some stranded alloys though are rated much higher)
does the NEC derate stranded wire with ends soldered into a crimp or solder end terminal.... nah.
electrons are known to move on the surface of the wire though...so it would seem that finely stranded wire, with much more surface area would carry more current than the same diameter solid wire.... but it isn't.
this is no doubt a factor though, apparently not the primary factor. accordingly soldering the ends of stranded does not reduce its current carrying capacity at least not according to the NEC and common practice.
On Fri, 10 Feb 2006 13:42:02 -0800, "Phil Scott" Gave us:
Surface area means nothing. Circular mils is not a measure of surface area, but one of cross sectional area.
You're an idiot. Other than silver, any alloy with copper will have a LOWER ampacity than pure copper.
You are an idiot. That doesn't make it right or acceptable just because they do not specifically address your rambling bullshit.
Not true. Only in high frequency applications. At AC power frequencies, it is *near* the surface. In DC applications, it is throughout the conductor..
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You're an idiot. All the strands would have to be insulated from each other as in Litz wire. A stranded copper wire acts just like a solid copper wire except is has a slightly lower circular mil area for a given gauge, making it have a slightly LOWER ampacity, so your first remark here is wrong as well.
You need to go back to school and touch up on what you apparently didn't pay much attention to begin with.
It isn't about their ampacity, it is about the physical and mechanical properties of a solder drenched stranded wire under the stress of a compression connection or crimp lug.
How much real "surface" is there when the strands are all crammed together? Doesn't the usable amount of surface diminish when the surfaces are touching one another? Current concentrates on the surface, but doesn't travel there exclusively. Part of the factor in rating wire is also it's ability to conduct and dissapate heat. Stranded wire has a harder time dissapating heat away from hot spots in a circuit. That might have something to do with it.
On Sat, 11 Feb 2006 03:30:36 GMT, "Long Ranger" Gave us:
Damn! you may actually be guessing right about something!
It looks like you are both stuck on surface area. Not related to ampacity.
Wrong. Stop posting FUD.
Hahhaha... Do either of you know ANY electronics?
No shit.
Are you sure about that? Stranded wire gets rated for less ampacity because it has a slightly lower circular mil area... you know... the one that DOES count!
Hahahaha...
You to laymen are meant for each other.
Both of you need desperately to take some electronics studies. If you DID take some, you were either asleep or your brain has since gotten befuddled. Try again, boys.
"John Ray" wrote in message news:ueednfDf2dkUvXPenZ2dnUVZ snipped-for-privacy@comcast.com... : : "Phil Scott" wrote in message : news:dsj1fr$ifj$ snipped-for-privacy@news.tdl.com... : : : > electrons are known to move on the surface of the wire though...so it : > would seem that finely stranded wire, with much more surface area would : > carry more current than the same diameter solid wire.... but it isn't. : >
: : : > Phil Scott : >
: Your referring to skin effect, and its frequency dependent, as the higher : the frequency, the more likely it is to travel along surface area. At : 50-60Hz its essentially a non-issue. : : John : : Over the last decade or so "skin effect" has taken a beating as to its intended definition, unfortunately. A lot of the lower echelons recall "somewhere" reading about the volume of electrons moving in a wire, and if you break the cross-sections into rings, the outer ring (obviously) contains more area and thus can have more electrons/holes whatever you want to call it these days. So they semi-logically jump to the conclusion of "Oh, that's what skin effect is" because it's a concept that's more easily understood. I had quite a discussion with a high school teacher once who was teaching skin effect that way with absolutely no basis of fact; it was a "jazzy" word the kids remembered, he explained, after he realized I might know something about it, and said if it helped the kids remember the cross-sectional studies, then it was a minor "error" that worked. He said. I have to wonder just how often that's happened and how prevalent it really is. He wouldn't back down either, but for at least the rest of the time he had our foster kid in his class, he never used the term "skin effect" again, so all was not lost. I managed to provide the kid with a concept he could understand, but that teacher, well, there was no way he could be wrong ! I can still see the blank look on his face when I started to talk about waveguides and how they worked . Back in "the day" when I was able to work, I recall some animated discussions about skin effect and where it began to take on accountable effects that could be measured. We asked out resident scientist to help us out with it once, and we all felt like we'd been put back in school to study field theory; woof!
Rather, at 50-60Hz and with wire diameters likely to be used with terminal lugs or screws it is negligible. In high power applications with very large conductors carrying high currents it can become a factor, even at power line frequencies.
I'm probably running the risk of dragging some bull into this but here goes. My researches dug up this little lot ( I posted in another tree but the whole arguement got really messy for some illogical reason). We know what I'm talking of so maybe we'll leave it at that :o) *mops brow*.
I'll throw some ideas at you, and some titles, my apologies, I don't have any net citations (I tend to learn from books especially if it's scientific technical), but I'll quote from my textbooks. More if you wish.
Think of rubbing an ebonite rod with dry fur.
"An ebonite rod which has been rubbed with dry fur attracts light bodies, such as small pieces of paper, and it repels another rod which has been treated in the ame way. A glass rod which has been rubbed with silk also attracts light bodies, repels another glass rod which has been similarly rubbed, and attracts an ebonite rod which has been rubbed with fur."
"A negative charge placed at any point on an insulated conductor repels electrons in the material to all parts of the surface, while a positive charge at any point attracts electrons from all parts. That is, a charge placed anywhere on a conductor effectively spreads all over it, because the electrons in the material itself are free to move. Insulators do not contain free electrons, and electrons are not easily seperated from their positive nuclei; so a charge placed on an insulator does nt spread over its surface. Ebonite, glass, mica, paraffin wax, sulphur, and dry silk are among the best insulators. Dry air and dry gases generally are good insulators in ordinary circumstances; moisture in a gas or on the surface of a solid reduces the insulating properties greatly. Electric forces act *through* (itallicised in the text) insulators, which when spoken of in this connection are called
*dielectrics* (itallicised in the text)."
Think of the Gold Leaf Electroscope.
Charging by induction.
The Electrophorus.
Faradsy's "ice-pail" experiment.
Distribution of potential and charge over the surface of a conductor.
Capacity. Condensors.
Displacement currents. "Maxwell defined the displacement current as *the quantity of electricity which is caused to pass normally through one square centimetre of the dielectric on account of the electric intensity*. If there is a surface density of charge of Q ESU per sq. cm. on the plate A, a charge Q moves across each square centimetre of the dielectric from A to Z, so *the displacement D in the medium is equal to the surface density Q on the charged plate*. The electric intensity, as the cause of the displacement, is analogous to mechanical stress, and the displacement to mechanical strain. The energy stored in unit volume of a mechanically strained elastic medium is 1/2*(stressxstrain). The electrical energy stored in unit volume of the medium is similarly 1/2x(intensityxdisplacement), or 1/2ED."
(confuses my concept somewhat)
Wimhurst machine.
Van de Graff generator.
Gauss's Theorem.
- Intensity due to an isolated charge conducting sphere (pg 35)
- Intensity close to the surface of a conductor (36)
- Force on the surface of a charged conductor (36) "The charge resides entirely on the surface, and the reason why the charge on any element is held there is that all the other charges from all over the conductor combine to produce an intensity directed outwards which holds it there. Further, as there is no intensity inside the conductor, the intensity due to the charge on the element must just cancel out that due to all the other charges at points inside the surface." goes on to say "... It remains to reconcile the two results..."
Law of inverse squares.
Definition of the absolute EMU of current "that current which, flowing in an arc 1cm. long of a circle of 1cm. radius, produces at the centre of the circel an intensity of 1 oersted." "The practical unit of current, called the ampere, is one-tenth of the absolute unit. " cf pg(110 and 323)
Textbook of electricity and magnetism. G.R. Noakes MA (Oxon) F.Inst.P.
(a man who could express himself without using the word 'fucktard' or 'retard' or any other derogation I can find).
London, Macmillan. 3rd edition. 1956. Maybe the times have changed.
A study of the fuse would likely be good.
Oh and Roy, before you explode like a fool, you are sacked as a tutor. Maybe I'll write you a new standard.
I feel sorry for the Original Poster, the s**te posted in here so far may have scard him off for life. "wow, look what I've done now" he thinks as the bar-room is trashed and the ladies run for cover.
I'd be interested too, I posted what I said because of studies I did while working for Philips components; working making magnets with some really illuminating chemicals, the stuff used was hydrophilic and pyrophoric, it combusted when we poured Vmto onto it! They use our little magnets inside computer Hard Dives now. The studies weren't reqired for the job, but they were interesting none the less.
An very interesting observation and one to be borne in mind.
A study of the 'mechanical equivalent of heat' and of resistance (for it is resistance which causes a wire, or most other electrical component to generate heat) would elucidate why.
I suppose any designer of electrical circuitry worth his salt would understand this but I must add, it's probably not always relevant to run of the mill applications e.g. hobbies and household stuff. The wires are general and likely not to burn out.
Cheers Phil, it's an exciting topic, not always relevant, but interesting nonetheless.
I suppose a soldered termination has more surface area than the outside diameter of the cluster of strands. And being a cluster of twisted strands the electrons have a route onto the soldered *unified* termination. Question is, how much *conceptual* extra area is created by the solder?
Answer
No of strands x circumference of each strand x length of soldered termination = Area of termination available to transfer electrons before solder applied.
Circumference of soldered termination x length of soldered end = Area of termination available to transfer electrons after solder applied.
N.B. this applies to terminations which have the twisted strands fully 'immersed' in solder to unify them.
I'm searching but can anyone help me out with info on the sizes (diameters would be really helpful) for strands within these wires? A comparison could be done between the capacities of the 'twisted strand cables' and the soldered terminal could be begun when this info is found.
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