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Wire questions

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I

ichthos

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As I am sorting out my wiring problems, I realize I need to know a little bit about wire itself. I needed to get some of the purple/white wire that melted. I contacted British Wiring, who is sending me some of the wire I need for free (Thanks for the info, Don.)They wanted to know the gauge of wire I was using and all could do is tell them how many strands it had - 14. That is all they seemed to need. So, is that how you tell what gauge wire it is by the number of strands? If so, how do you know what gauge a solid wire is? Any information would be appreciated. You guys might just get me educated yet.
Kevin
 
Number of strands is the British way of doing stranded wire sizes. Sometimes they also give the diameter of each strand (eg 7/0.2 means 7 strands of 0.2mm diameter), but usually it is assumed.

Most often in the US, wire size is given in "gauge", which refers to American Wire Gauge or AWG. This is a magic number based on the overall diameter of the conductor, whether stranded or solid. Oddly enough, the AWG number gets bigger for smaller wires.

British Wiring has a brief summary at
https://www.britishwiring.com/CAT02_07.PDF
 
I had figured the numbers in AWG got larger possibly because it was actually part of a fraction - kind of like f-stops in a camera. You said that in the US, the gauge is expressed as AWG. What designation do the British use?
Kevin
 
No, I am not putting in solid wire. And sorry Randall, I did not see the hyperlink. My time was limited on the internet, so I was going through things fast when I went to the British Wiring site that you referred me to also, Don.
 
Not to be smarty but to be exactly correct, AWG stranded wire is a tini bit larger in dia. than solid wire, due to the air gap bewteen strands. Also, smaller AWG wires get larger in its designation number because originally the smaller wires required more passes ( in a rolling mill, not sure ??) to reduce its size.
Robert
 
That's interesting, Robert, I didn't know that. I always thought the outside diameter remained the same, and the resistance per foot was slightly higher. Thanks for straightening me out.
 
Many charts show slightly different resistance for stranded wire. Supposedly because the individual strands travel a longer path than the overall length of the bundle. For example, the chart at https://www.seas.gwu.edu/~ecelabs/appnotes/PDF/techdat/swc.pdf (just the first one I found with Google) shows different resistances even depending on how many strands there are! (More strands = longer path).
 
Going back 45 years to my Electronic Theory days.....electrons travel on the outside of the wire. Multi-strand wire has far more outer surfaces, and will pass more current. That is 45 years old, and subject to similarly aged memory.
And, I am very pleased you are not using solid wire.
 
I believe the 'skin' effect only applies to AC. And it depends on frequency, so it's hardly noticeable at 60 Hz. At radio frequencies though, it becomes so strong that a hollow tube has the same impedance (resistance to RF) as a solid conductor.
 
I give up..there is too much knowledge in this post :smile:.

Updating my previous post , Yes, I was " legally incorrect " incorrect as the resistance in stranded copper wire is a bit higher than solid wire...but it is very insignificant , maybe 0.0001 ohms per meter, from one of google charts I just read.

Robert
tr4a irs
 
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