How much current does AWG 24 wire carry?

[eeguy]

Hello, different sources provide different answers. One stated 0.577A. The other 7A, etc. Which is correct?

[jpanhalt]

Current rating reflects allowed temperature rise and is affected by insulation and packing.  In free air for bare wires, this table indicates about 800 mA to 900 mA:   https://www.pupman.com/listarchives/1998/April/msg00222.html

Edit: Fixed link

[ejeffrey]

Both, or neither. It depends on how it's used.

Here is one table: https://www.powerstream.com/Wire_Size.htm

It lists the limit as 3.5 amps for "chassis wiring" which is a single insulated wire in air, 0.577 amps for "power transmission" which is a bundle of wires.   Bare wire can conduct more, and different insulation has different temperature limits.  Short wires where a lot of heat is dissipated through the ends can condict more.  Wires in a potted enclosure can carry much less.

[IanB]

In addition to thermal limits, you may in some cases be concerned about the voltage drop in the wire, especially over long runs.

[CatalinaWOW]

In addition to the factors which jpanhalt mentions, which affect how hot the wire gets, different safety standards can affect this.

One source may be quoting the current at which the wire melts (which is also affected by the specific alloy), another may restrict the temperature to the softening temperature of the insulation, and yet another may keep the temperature below what is safe to touch.

If you don't have the tools to evaluate all of the factors involved I would restrict current to the low end of the recommended ranges.  Wire is cheap.  Burns and fires are not.

[eeguy]

Thanks.

I saw a stepper motor has a rated current of 2.1A. The four wires coming out of the motor are non-removable. I asked the manufacturer the AWG value and they said 24. Does each of those four wires considered to be a "bundle of wires" which means they are limiting the full potential of the motor as only 0.577 amp will be supplied to the motor?

I got a Meanwell LRS-250-24 power supply. Now I am choosing:

- power cord (AWG18 vs 14)
- wires between the IEC320 C14 Inlet Module with switch and the power supply
- wires from the power supply to motor controller.

For these power cord and wires, is it better to use AWG 18, 16 or 14?

[Siwastaja]

You have seriously misunderstood something. Wire thickness has nothing to do with the current it will carry. In a stepper motor specifically, it will carry the current your stepper motor driver is configured to use. You can pass 1000000000A through that wire. The only question is if the wire gets too hot while doing that, to the point of the insulation melting or catching fire. Normally you would believe the manufacturer has done their engineering properly and the specifications can be trusted without asking questions about such design details, but of course some amount of derating is usually helpful for maintaining long life.

[eeguy]

You have seriously misunderstood something. Wire thickness has nothing to do with the current it will carry. In a stepper motor specifically, it will carry the current your stepper motor driver is configured to use.

In the past, a senior at school told me that the thicker the wire, the more the current it could pass through. That is where I got that idea.

[Coordonnée_chromatique]

https://www.engineeringtoolbox.com/wire-gauges-d_419.html

[Siwastaja]

You have seriously misunderstood something. Wire thickness has nothing to do with the current it will carry. In a stepper motor specifically, it will carry the current your stepper motor driver is configured to use.

In the past, a senior at school told me that the thicker the wire, the more the current it could pass through. That is where I got that idea.

Yeah. This underlines how important it is to be exact and include as much information as possible. What they failed to tell you, or you misunderstood, was this important piece: "without damage".

Usually, ignoring going to extremes, the wire would not actually control or limit the current. The current would be defined by the rest of the circuitry - in your example, by the stepper motor controller - ; then the job of the wire is to be thick enough to survive the current without smoke, and also thick enough to minimize unwanted losses. If the wire is short, then it's usually more about survival than losses, but for long wires losses start to matter even if heating is modest.

[pcprogrammer]

You have seriously misunderstood something. Wire thickness has nothing to do with the current it will carry. In a stepper motor specifically, it will carry the current your stepper motor driver is configured to use.

In the past, a senior at school told me that the thicker the wire, the more the current it could pass through. That is where I got that idea.

In principle this is correct, but:

Current flowing through a wire is basically based on two things, the voltage and the resistance. A thicker wire has less resistance than a thinner one, but length also plays a role. A short wire has less resistance than a long wire of the same thickness. The material the wire is made from also plays a role.

So it depends on all these properties what the resistance of a wire is and that will determine how much power is going to be dissipated in the wire. P = I^2 * R. Throw time in the mix and this will lead to a temperature rise of the wire.

Your stepper motor has windings that are rated for 2.1A, so this current will also flow through these four 24 AWG wires, but they are short and won't have much resistance. So the power dissipated in the wires won't be a lot.

It might well be that the rating you found is given per meter of wire.

[iMo]

..You can pass 1000000000A through that wire..

Can an AWG 24 wire conduct 1000000000 Ampers?

ChatGPT:

No, an AWG 24 wire cannot conduct 1 billion (1,000,000,000) amperes. The American Wire Gauge (AWG) system is used to standardize the diameter of round, solid, nonferrous, electrically conducting wire. A higher gauge number indicates a smaller wire diameter. AWG 24 wire has a diameter of about 0.51 mm (or 20.1 mils).

The current-carrying capacity, or ampacity, of a wire depends on various factors including the wire's material (usually copper or aluminum), insulation type, the ambient temperature, and how the wire is installed. However, the ampacity of an AWG 24 copper wire is typically around 3.5 amps for chassis wiring (short, exposed runs) and about 0.577 amps for power transmission, according to the National Electrical Code (NEC) and other guidelines, assuming a temperature of 20°C with no additional heat sources.

Conducting 1 billion amperes through a wire would require a wire of an enormously larger size and would also involve substantial infrastructure to manage the immense heat generated and magnetic forces produced. Such currents are far beyond the scope of practical electrical wiring and are not encountered in conventional electrical engineering or power distribution systems.

[IanB]

Can an AWG 24 wire conduct 1000000000 Amperes?

This is where ChatGPT falls short. The question is not "if", but "for how long?"

Certainly the wire will vaporize, but in order to vaporize, it had to be carrying that current for some minimum time like a nanosecond before that.

[eeguy]

Your stepper motor has windings that are rated for 2.1A, so this current will also flow through these four 24 AWG wires, but they are short and won't have much resistance. So the power dissipated in the wires won't be a lot.

It might well be that the rating you found is given per meter of wire.

 
The company told me that the wires from the motors are 500mm(UL1007 AWG24).
So, what wire gauge is recommend for the power cord (AWG18 vs 14),
wires between the IEC320 C14 Inlet Module with switch and the power supply as well as
the wires from the power supply to motor controller (one could output 4.2A and the
other 5.6A, not decided which to get yet)?

[baldurn]

Besides all that, the motor is not going to be drawing 2.4A continuously through one set of wires. I would expect the average to be half of that maximum.

[golden_labels]

Continuing with the jocular tone, I say it’s not “for how long” but “if”. With gigaamperes we may need to treat a wire as a transmission line just to account for it evaporating before it starts to fully conduct.

Quick, somebody ping Veritasium or AlphaPhoenix to answer the question. We need another epic YouTube creators argument!

[themadhippy]

just chuck it in the freezer until it reaches 0 kelvin an it should be good for few  billion amps

[golden_labels]

Slightly, but only slightly, more serious tone now.

Resistivity of metals is ρ ≈ 10^-8 Ω·m. With the cross-section area of about 10^-7 m², we get resistance of 10^-1 Ω/m. To get 10⁹ A current, the voltage across a meter of a wire would need to be 10⁹ · 10^-1 (A·Ω/m) = 10⁸ V/m.

So you will need a pretty good isolation materials and geometry to produce 1 GA.

[baldurn]

Continuing with the jocular tone, I say it’s not “for how long” but “if”. With gigaamperes we may need to treat a wire as a transmission line just to account for it evaporating before it starts to fully conduct.

The wire is just there to get the spark going. As soon as it arcs over, the wire is no longer needed.

[T3sl4co1l]

Can an AWG 24 wire conduct 1000000000 Amperes?

This is where ChatGPT falls short. The question is not "if", but "for how long?"

Certainly the wire will vaporize, but in order to vaporize, it had to be carrying that current for some minimum time like a nanosecond before that.

Actually, I would dispute that this is possible at all: consider the dI/dt required to reach such a current even in such time scale where the wire might possibly not immediately vaporize.  Likely the voltage drop is sufficient to break down in air at the very least, and most likely cause field emission in vacuum too.  The wire (and any insulation covering it) would quickly be consumed by the resulting plasma, and, I suppose, fully ionized in the process; the voltage drop might actually rise because no more free electrons are available.  Eventually pair production would occur, stabilizing the voltage drop; or nuclear reactions.

For reference, the Z-machine does ca. 26MA, triggering nuclear reactions.  The focus is, I think, a bit smaller than a 24AWG wire, but depending on length in question, perhaps it is comparable.

So, we can, with a little confidence, rule out currents quite this high, I think.

Continuing with the jocular tone, I say it’s not “for how long” but “if”. With gigaamperes we may need to treat a wire as a transmission line just to account for it evaporating before it starts to fully conduct.

Worse, not only would TLs be required to even begin to attempt such an experiment, nuclear physics gets involved, too.

...

As an exploding bridgewire, I think on the order of ~10kA and <1us, skin effect dominates, concentrating the power dissipation in the surface, and ~instant vaporization can occur; at lower dI/dt, probably this current is survivable, up to, oh I don't know, maybe 100s µs, 1 ms or so?  Beyond which, (bulk) melting and vaporization occur rapidly.

These are fairly -- well, not common, but plausible, let's say -- induced-lightning surge currents, within the realm of commercial or industrial practice.  Somewhere around here might be considered the ultimate limit for such wire.

...

Anyway, yeah.  For continuous or intermittent use, you can jam practically as much current as you want, until the wire heats up too much.  The real question is, how hot is acceptable?  How much voltage drop?  Wiring tables assume some condition (limiting temperature at worst-case power dissipation capacity, e.g. wires in conduit in insulated wall space), so tend to be highly conservative.  Chassis wiring is typically short and has good air circulation, so that more current can be passed for the same temp rise -- note that short wiring length, besides keeping the voltage drop down, also can provide some heat sinking out the ends of the wire, heat flow is not strictly radial (out of the wire surface) but lengthwise as well and therefore different assumptions apply.

Which is similarly relevant for PCB trace width calculations: it's practically irrelevant if the length is short or the aspect ratio isn't monstrous, and mostly matters on long narrow routes where heat flow is lateral.

Connectors add a whole 'nother wrinkle, as they might be rated more-or-less what the wire is, but the contact point(s), pressure, plating, temperature range, temp cycling, and mechanical vibration, all play a role in their endurance.  Failure typically occurs when contact resistance increases too far, and the pin burns up.  This can take merely hundreds of mechanical cycles (for poor quality or mismatched plating), and may be exacerbated by current flow (heating, electromigration).  High-current connectors typically have multiple contact points -- contacts designed with multiple leaf springs, usually with a bump projecting from the surface into the terminal/post to concentrate contact pressure, and this takes up both mechanical tolerances and helps ensure consistent contact under motion.  That said, I've seen ratings from 2 to 5A for headers in the style of Molex KK 0.1" series -- the upper range I believe by Sullins, though I don't recall their terminals looking any different from Molex's. 

Tim

[Jwillis]

Wire can carry a lot more than what is considered the acceptable standard. https://en.wikipedia.org/wiki/American_wire_gauge. The UL and CSA standards give a more detailed description of the current capability of transmission lines based on the number of bundles. The NEC will have their own standards based on the type and capability of the insulation.
How and at what current a wire fuses at depends not only on the gauge but also the type of conductor used. Aluminum wire will fuse at a lower current than cooper for example.
Theirs no rule that states that you can't pull more current through a wire than what is considered standard. It depends on what you would consider and acceptable voltage drop and temperature rise of the wire for your experiment. But your not going to instill much confidence in you project or product if it's smoking or on fire.

[mag_therm]

Theirs no rule that states that you can't pull more current through a wire than what is considered standard.

Yes there are such regulations based on C.S. Area, for installations covered by the Electrical Wiring standards in most countries.

But if you design equipment such as transformers, the standards are not based on conductor sizes.
However safety is then covered by insulation temperature rise standards.

[alligatorblues]

Iin the USA, RESIDENTIAL wiring is one gauge larger than standard ampacity in any other application, because most homes lack fire suppression, and electrical is the most common cause of house fires. Whithin the shroud of electric using appliances, the figure for house wiring halves, so if you can use use 14AWG for 15A in residential building, inside a manufactired device, it can be used to carry up to 30A. 

The smallest 120VAC wiring is 14 AWG, because it's the smallest that can withstand the tensile force of fishing in conduit. After 14AWG, 16, 18, 20, etc., the rules completely change. 28AWG is industrially rated for 800mA. However, a main concern is preserving insulation and preventing injury, property damage and/or equipment failure. As long as none of that happens, it's cool.

My uncle works in installation and maintenace of UPSs. In one data center, there was a room full of manual maintenance lead acid batteries, with a 20 year life. But they had to be checked for output voltage, and have water  added. One of the guys working on those batteries lost his balance. The room was 20 feet high. So, they needded planks. He hit those terminals just perfectly. He was instantly fried. Another guy was working on 480 3ph, and there's these things called tin whiskers, where tin-finished and tin soldered electical devices grow projections sometimes 10mm long. Once in a while a tin whisker will complete a short circuit, causing a cataclysm of vaporized metal flying in all directions. Usually they just melt away. But if another short is caused by the first one, a whole breaker panel can explode.

That happened to my uncle. A 480 3ph junction box just exploded, leaving not a trace. He had a visor on and a Nomex suit.

These ups's have so much power, ATT put 25 750kva units for one of their data centers. The load used to test it had to be carried on a semi trailer.     

Got off track. Silicone and Teflon, 2 very chemically inert and heat resistant insulations can raise ampacity 2-3x over Romex or pvc insulation. Ampacity is based on heat production and ability to withstand it. A wire is a resistance. The thinner the wire, the higher the resistance.

From V=IR, the lower the Ohms, the higher the current. 120V driving current through a resistace of 1.2 ohms will produce a current flow of 100A. 120/1.2=100. Soft, annealed, pure copper 24 AWG wire has resistance of 0.026 Ohms per foot.

If you're using a drive voltage of 24VDC through 5 feet of 24 AWG copper wire, R=0.13 Ohm. 24VDC/0.13 Ohm=184A for a short circuit. P=I^2R; 184^2=33856*0.13=4401 Watts. So, you get a little idea of how these three basics interact.

Joules are energy. This unit can be expressed  in many ways. But one is:  the work required to move 1 Coulomb of electric charge through one volt (C*V). The ampere is 1 Coulomb/second. Watts are power, or Joules/second. And Kilowatt-hours are Joules. 1 kW*hr=3.6 million joules. If you assign units  to your operands, you always know if the result is correct, because the answer is in the correct unit. 

So, you have to learn how to choose your wire. I use 18-22AWG silicone insulated hookup wire for almost everything. It's really nice to work with, and I don't use much, so cost isn't a factor.

[ejeffrey]

Thanks.

I saw a stepper motor has a rated current of 2.1A. The four wires coming out of the motor are non-removable. I asked the manufacturer the AWG value and they said 24. Does each of those four wires considered to be a "bundle of wires" which means they are limiting the full potential of the motor as only 0.577 amp will be supplied to the motor?

No this should be fine.  The wires are short, and while they may be 4 wires "bundled" that's not the same as a 2" diameter  conduit stuffed full of wires running for 100 feet.  2.1 amps is fine for this sort of thing, especially since only one pair of wires will be carrying the max current at any given time.

I got a Meanwell LRS-250-24 power supply. Now I am choosing:

- power cord (AWG18 vs 14)
- wires between the IEC320 C14 Inlet Module with switch and the power supply
- wires from the power supply to motor controller.

AWG 18 is fine for all of those purposes.

[eeguy]

Thanks.

I saw a stepper motor has a rated current of 2.1A. The four wires coming out of the motor are non-removable. I asked the manufacturer the AWG value and they said 24. Does each of those four wires considered to be a "bundle of wires" which means they are limiting the full potential of the motor as only 0.577 amp will be supplied to the motor?

No this should be fine.  The wires are short, and while they may be 4 wires "bundled" that's not the same as a 2" diameter  conduit stuffed full of wires running for 100 feet.  2.1 amps is fine for this sort of thing, especially since only one pair of wires will be carrying the max current at any given time.

I got a Meanwell LRS-250-24 power supply. Now I am choosing:

- power cord (AWG18 vs 14)
- wires between the IEC320 C14 Inlet Module with switch and the power supply
- wires from the power supply to motor controller.

AWG 18 is fine for all of those purposes.

Thank you. I proceed to order then.

[Jwillis]

Theirs no rule that states that you can't pull more current through a wire than what is considered standard.

Yes there are such regulations based on C.S. Area, for installations covered by the Electrical Wiring standards in most countries.

But if you design equipment such as transformers, the standards are not based on conductor sizes.
However safety is then covered by insulation temperature rise standards.

The code only describes how the wire is to be installed. But does not regulate how it is to be used after installation. The NEC and UL/CSA  does not regulate end use. 

[pcprogrammer]

So, what wire gauge is recommend for the power cord (AWG18 vs 14),
wires between the IEC320 C14 Inlet Module with switch and the power supply as well as
the wires from the power supply to motor controller (one could output 4.2A and the
other 5.6A, not decided which to get yet)?

The power cord is a different story. It connects your power supply to the mains, which for you probably is 120V. If the stepper motor runs an average of 1A at 12V the current on the power cord is only in the order of 12 / 120 / efficiency of the supply (maybe 90%) part of the output current. So ~111mA. But there will be peaks to take into account. A standard power cord (AWG18) will do.

For the wires in between the power supply and the controller you can use something in between AWG24 and AWG18 depending on the length of the wires.

As for the actual current flowing through the wires it depends on a lot of factors. Measure the DC resistance of a single winding and divide the supply voltage by the resistance. This tells you the max current that can flow. Then there is AC behavior of the motor. To make it run the windings are actuated in turn, and this means pulsed voltages, reducing the average current.

To get a better understanding of it all I would suggest to read up on the basics of electrical engineering.

Edit: During my morning walk it dawned on me that I have the efficiency calculation wrong. Instead of multiply it should be divide. Amended the formula and result.

[soldar]

As a very rough starting point, rule of thumb and sanity check I use a guide of 3 A/mm2 for things like transformer windings and 10 A/mm2 for residential home wiring.

[soldar]

You really have to wonder what were they thinking when they invented the AWG

[johansen]

You really have to wonder what were they thinking when they invented the AWG

(Attachment Link)

its really not that bad. they were working with what they had at the time, which was various competing companies offering wire in different sizes.

By definition, No. 36 AWG is 0.005 inches in diameter, and No. 0000 is 0.46 inches in diameter. The ratio of these diameters is 1:92, and there are 40 gauge sizes from No. 36 to No. 0000, or 39 steps

of course they could have arbitrarily definied 0000 as .5 inches and made the math slightly easier, with no practical functional difference for anyone who actually works with their hands.

[Psi]

+1 for the powerstream table.

3.5A for wiring inside a device
0.57A for getting power somewhere.

It's more about heat and Vdrop, if you're ok with how hot the wire gets and the voltage drop then it's fine.
Wire with silicon insulation allows you to run it hotter.

Also if you coil the wire up you have to derate it because you have hot wire next to hot wire next to hot wire. So the hot wire in the middle sees the wires either side as ambient temp and so its temp shoots up from that point, not from actual ambient temp.  eg You get into runway very fast when you coil wires together.

[donlisms]

I think the AWG was heavily influenced by the Brown&Sharp gage that came before it. They chose two sizes that were clean sizes, (0.460 and... something) and then interpolated for the intermediates, and then rounded things off here and there.   The NBS has some papers that explain it all, with the general conclusion that it works just fine, given all of the other uncontrolled variables, eg how the wire is drawn, and the composition of the copper alloy, and all that stuff. Plus .34% per degree Centipede, of course.  All of this gage stuff is approximate, especially when you consider the resistance, which is where the real issues are.

History.  "Yes, Tommy, this is how we got here."

[inse]

Q: How much load can a donkey carry?
CQ: On the flat or up the mountain, for 5min or 5h, with PETA involvement or without?

[johansen]

Q: How much load can a donkey carry?
CQ: On the flat or up the mountain, for 5min or 5h, with PETA involvement or without?

i would love to see some of the armchair electrical engineers take apart their oven or range, only to find that 16 gauge wires run 14 amps through a 3500 watt oven heating element. oh the horror.

you can get about 3 pounds of wire out of them these days. good quality 105C rated wire. good for fixing cars and shit.

[coppercone2]

I think some of these values are nuts.

What exactly are you doing? the manufacturers need to COVA their ass.

I am lookin at a curve, at 35C above ambient for a single strand you get 3.75 amps. For a cable of four you get 2.8 amps.

If you have 80C rated cable, and your in normal places, you are still 45 C short of getting to the actual cable rating.

Then you have deviations like color of the cable, how its routed (race way or hanging in the air?).

If you are selling something to people you wanna definitely obey this stuff. If you are doing it for yourself then you have some leeway, so long you follow some precautions, like setting fuses. Different loads are different, how well behaved is your load? Can it stall out and draw massive amounts of current? Do you have a hard fuse or a poly fuse or a circuit breaker that you might keep resetting? What is the run time of your device?


For instance welding machine work cable is so different then NEC! 


If you followed NEC for welding machine work cable the results would be preposterous beyond belief.


I used a 20 AWG 4 strand cable with 80C rating to carry 12 amps! 

What is the result on this black TPE cable? After an hour of run time the cable gets warm to the touch. Its connected to a machine that makes alot of noise and its hanging in the air in a spiral shape. IF I take this machine out in the hot sun and let it run indefinately on the hottest day of the year, we might get close to the rating. The cable rating guideline is 0.8 * 6.5 amps (4 strand on 6.5 amp rating for single strand), aka 5.2 amps per wire, doubled up lets call it 10 amps. I ran it on 12 amps.

The table does not factor in the color, which has an effect on dissipation. This cable is braided with bare copper, no foil. The table just says to ignore shielding. Is this correct? Who knows. I imagine a braid might insulate this less then a foil. Maybe it just assumes insulated foil.


So oh no, I am running at 120% overload!!!!

But what does my hand tell me ? in a room temperature enviroment this cable is slightly warm after 2 hours. If it was zip tied into a strain relief, or jammed super tight inside of a cable routing thing inside of a box I might think hmm can this cause a problem??

 When its floating in the air my analysis tells me that its safe enough for a loud specialized tool that might run for a few hours of supervision. Am I going to redesign this for 18 AWG? NO! I am happy with it! Would I sell it ? No, because someone might get upset. But in my case this lab machine runs just dandy and there is IMO No hazard.


For a different example, a spot welder. It has 8 AWG silicone wire. I have to handle the wire and electrodes with my hands to use it. It welds at 1500 amps. If I use it alot, the wire gets hot. Hard to touch. If I was going to automate this machine I would up the gauge if its being used heavy because it gets seriously hot (but it goes into thick copper bus bars in the machine). is 8 AWG wire the wrong choice for 1500 amps? No, it makes sense for k-weld. Infact its what the manufacturer supplies you with! Would making thicker cables improve quality? Maybe, maybe not. The dexterity offered by the thinner wires might allow for better more repeatable probe position and more repeatable spot welds. If I am fighting heavy cables so the wires don't get hot, I might do it wrong and compromise the weld. Logically I think I should just leave it be!


How about my tig machine? If the wire gets hot on your leg then let it rest! No NEC here! Its not even a normal wire. They route argon through the weird super flex braid to cool it. So its a wire inside of a gas tube that cools when your passing tons of current through it. Leave it to manufacturer to decide.


How about my wall outlet? You bet your ass I won't deviate from the NEC recommendation when its powering welding machines and it deserves some extra copper! no fooling around in the wall

[MrAl]

Hello, different sources provide different answers. One stated 0.577A. The other 7A, etc. Which is correct?

Hi,

The question of current capacity for a wire is not just one about wire size and current alone, it's also about the application it is to be used in.  The application requirements include knowing a lot more than just the wire size and current capability.  That's because there are other factors involved sometimes like length, ambient temperature, temperature rise, wave shape of the signal, etc.  Sometimes an application is associated with a certain wire area per ampere to make the choice of wire size a little easier.
In the table attached, we can see wire size 24 and a current rating of 0.67 amps 'I' at 600cm per ampere.  That would be for a regular hook up wire that is not especially long.  If the wire was used inside a transformer though, we may have to increase the area to 1200cm per ampere which would mean wire size 24 would only be good for half that current around 0.33 amps.

There are a lot of other factors however.  In a transformer there is also skin effect, which raises the AC resistance of the wire.  That's an entirely different calculation that involves the frequency of the wire.

What this all means is that you don't really ask how much current a wire can carry you ask what an application requires.  So you are asking more about the application than the wire.  In real life you study different applications and that comes with the knowledge of what wire specs are to be observed.

A typical application is an extension cord for a home appliance (or similar device).  These days attention to wire length is also included in this application specification.  #16 is good for some lengths but #14 is chosen if the length of wire is longer.  The reason is that voltage drop becomes an issue because the voltage at the end of the wire is less than the voltage at the beginning of the wire where it plugs into the wall.

It does not make too much sense to talk about a billion ampere current through a #24 AWG wire because for one, the fusing time is inversely proportional to the square of the current, and the square of the current is a very large number.  This puts the fusing time somewhere around 0.0034 picoseconds, and as you know 1 picosecond is 1e-12 seconds, a very small amount of time.  Even a million amps will melt the wire in about 3.4 nanoseconds (25 degree C ambient).

Very often though we talk about "hook-up" wire, which is usually a short run.  The table in the attachment would be good for this application.

As mentioned above about applications, sometimes you have to think about the extremes too.  A wire in deep space will stay cooler than a wire inside a thermal container like a cooler used to keep things cool during the summer.
To show how extreme this can be, a wire that is completely thermally insulated will heat to the melting point every time even with a current of just 1 microampere.  That's because even the small amount of heat will build up over time because it has nowhere to dissipate.

[pcprogrammer]

The one thing that stumped me at first with this AWG, not knowing about it and being a metrics born person, is that the larger the number the smaller the wire.   

Here we just use mm2, and for electrical house wiring it is 1.5mm2 for light circuits fused at 10A and 2.5mm2 for wall sockets fused at 16A. Simple, the bigger the number the more current it can carry. 

[MarkT]

You can pass 1000000000A through that wire. The only question is if the wire gets too hot while doing that, to the point of the insulation melting or catching fire.

No, that level of current is completely impossible, the magnetic forces alone would destroy it.

At 1GA flowing the power dissipation would be 10^18 times greater than at 1A, the only strategy to avoid vaporizing the wire is make the pulse less than a picosecond, which is completely impossible as light only travels 300µm in that time, much smaller than the wire diameter!!

There are at least two practical limits to max current, one is thermal, the other is the magnetic field being strong enough to explosively crush or snap the wire.

[TimFox]

The one thing that stumped me at first with this AWG, not knowing about it and being a metrics born person, is that the larger the number the smaller the wire.   

Here we just use mm2, and for electrical house wiring it is 1.5mm2 for light circuits fused at 10A and 2.5mm2 for wall sockets fused at 16A. Simple, the bigger the number the more current it can carry. 

Similarly, the larger the AWG number, the smaller the diameter, and the lower current rating.
It's a logarithmic measure, similar to dB:  a change of 3 AWGs means a factor of two in cross-section area and roughly a factor of two in current rating.

[CatalinaWOW]

The one thing that stumped me at first with this AWG, not knowing about it and being a metrics born person, is that the larger the number the smaller the wire.   

Here we just use mm2, and for electrical house wiring it is 1.5mm2 for light circuits fused at 10A and 2.5mm2 for wall sockets fused at 16A. Simple, the bigger the number the more current it can carry. 

Every system has its advantages.  Square millimeters can be expressed as a sensible number for wire sizes used in low power applications that aren't particularly tiny.  But need a change of units for very large sizes and very small sizes, or several characters of scientific notation.  The change of units is problematic.  Using square centimeters will trap the unwary because the conversion factor is not the kneejerk 10, but 100.

Right now the metric system wins.  Not for its intrinsic advantages, which are much smaller than proponents seem to think, but because standardization really is beneficial and at this point in time the metric world is much larger than the "English units" world.  And AWG isn't even a "English units" standard.  It could (an often is) square mils or circular mils which scales size with current as you prefer.

[golden_labels]

The one thing that stumped me at first with this AWG, not knowing about it and being a metrics born person, is that the larger the number the smaller the wire.   

Derives from the number of times a wire had to be drawn to obtain one that thin. Makes perfect sense, when you know the history of making strings for instruments!

[Harrow]

Yeah. This underlines how important it is to be exact and include as much information as possible. What they failed to tell you, or you misunderstood, was this important piece: "without damage".

Haha, this is the true part. Just for fun, I tried to see if I could use some very light speaker wire with my arc welder. So pulling close to 200 amps through some very fine wire. To my surprise, it worked absolutely fine. Then I looked down and saw that the wire no longer had any insulation on it and was glowing red. 

[Picuino]

Take into account the voltage drop in the conductors, multiplying the current by the resistance per meter and by the length in meters doubled (for 2-wire cable).

[MrAl]

Hi,

In the old days they had to draw the wire through separate dies because the wire would break if they went through only one die with a large diameter rod.  The rod was drawn through the die and that reduced the diameter.  It was found that if they tried to go too small in diameter from the size of the rod, the wire would break, so they had to use one die to get down to a lower diameter, then another die to get to an even lower diameter, then another die, etc.  Each die would decrease the diameter by something like 10 or 11 percent.
From what I understand, Brown and Sharp produced the first dies, and the wire gauge number reflected the number of dies the wire had to be drawn through in order to get that initial (probably standard) rod size down to a certain size.  Thus, wire size AWG 24 had to be drawn through 24 dies.
I would think this made it easier for people actually making the wire since all they had to do was know how many dies to use to make a certain size wire.

Today we can convert that into a logarithmic system.  The ratio of the largest diameter wire to the smallest is 1 to 92, and that is part of the math used to calculate wire size today.

Is it dumb to have to use that system today?  Well, these old standards are hard to break because they have been used for so long and are known and understood by so many people today.  Changing them could result in errors which could result in dangerous situations coming up by some simple misunderstanding.  Many people who work in various industries know what a #22 AWG wire is, as well as a #10 AWG wire.  They may not even know what the actual diameter is, but they are familiar with that wire size by its AWG number and what it is usually used for.
For other applications though there are other standards such as SAE and ISO.
There's also SWG for wire sizes.

Today they may do the wire drawing a little differently with new techniques, and it depends what kind of wire it is too such as copper or harder metal.

I am sure there would be a lot to read on the web about all this.

[TimFox]

It is now common practice in the US to use “gauges” that are logarithmic in actual size or diameter.
This allows the user to find a gauge size that is within a certain ratio of the desired size, just as the standard choices of resistors in an E24 series (which are stated in actual value rather than sequence number).
Besides wire gauges (AWG = American Wire Gauge, slightly different than the British SWG Standard Wire Gauge), there are various sheet metal thickness gauges and “number drill” sets.
In practice, with either a gauge series or a metric arithmetic series, you still need to look up the wire resistance and rating in an engineering table.
Also, using a drill table you will find recommendations for “number drill” size for either  American UN screw threads or ISO metric threads so there is little need for both an arithmetic metric or logarithmic number set of drills.
Of course, since 1 inch is exactly 25.4 mm (by act of Congress), there is also a metric expression for the diameter of each drill size or wire gauge.

[radiolistener]

it depends on how many voltage drop and how many heating power you allow for the wire.

For example, for a copper wire AWG24 resistance is about 0.0841976Ω per meter.
So if you use 10 meters AWG24 wire it will have 0.841976Ω and at 7 Amps it will have voltage drop = 7 Amps * 0.841976 Ω = 5.9V. You will lose power 7 V * 5.9V = 41.3W, this power will going to a wire heating. Is it ok for you?

[soldar]

Q- How much current would a AWG 24 wire carry if a AWG 24 wire could carry current?

A- A AWG 24 wire would carry as much current as a AWG 24 wire could carry if a AWG 24 wire could carry current.

[CatalinaWOW]

Q- How much current would a AWG 24 wire carry if a AWG 24 wire could carry current?

A- A AWG 24 wire would carry as much current as a AWG 24 wire could carry if a AWG 24 wire could carry current.

Might want to add this to the engineering humor thread.

[golden_labels]

Wire drawing through dies dates back to at least medieval times.⁽¹⁾ Both the technique and parameters of the process. It was a huge industry centuries before Brown&Sharpe. They couldn’t be the first or even at the frontier.

However, Brown&Sharpe were well known. Visibility alone is enough to be perceived as the norm. They were also influential and abusing standardization process to get market advantage aren’t a modern invention. Though these are merely a plausible guesses made on the spot — I have no evidence for either.

⁽¹⁾ Stephen Birkett and Paul Poletti provide an overview in “Reproduction of Authentic Historical Soft Iron Wire for Musical Instruments”, along with some nice source pictures.