Current Carrying Capacity of cables with different voltages

[iamgary25]

Does the current carrying capacity of cables change on what voltage your using??

2.5mm can carry 27a at 230v
would this be the same for 1000v
could someone please explaain this whole process please
Confused lol

Grant

p.s i'm a student

 

[telectrix]

current capacity depends only on the cable csa, be it at 12V, 240V, or 24,000V. it's the power transmitted down the cable that increases with voltage. so, for example 5A @12V is ( 5 x 12 ) = 60watts, but 5A @240V is 1200watts.

 

[Dizzy_Maskell]

Just the insulation of the cable that will need to alter according to voltage

 

[iamgary25]

ok so the insulation just needs the correct voltage rating, just like you'd do for selecting electrical equipment and the current is the exact same, just the power differs, so the high the voltage the less power you can use with it?

 

[Marvo]

Current flow is a physical quantity of electrons flowing though the wire every second. If one amp is flowing down a wire then 6.25 billion billion electrons are flowing down it each second. The number of electrons flowing is what causes the wire to get warm and this is the limiting factor, the voltage pushing them along makes no difference to this. Wires are rated according to their temperature limits, their maximum current is that which causes them to get close to this temperature.

As pointed out the limiting factor with voltage is how good the insulation protecting the wire is.

 

[Darkwood]

The good old classical explanation there marvo ....il resist getting all quantum and correcting it as its good enough for the OP to get an understanding

I was tempted though but your a super power now with an urge to test your abilities :30:

 

[Silly Sausage]

Ah...I can see the 'What is electricity' discussion looming on the horizon.
I'm out!

 

[Darkwood]

Na not today Archy its quiz night at the local

 

[Marvo]

The good old classical explanation there marvo ....il resist getting all quantum and correcting it as its good enough for the OP to get an understanding

I was tempted though but your a super power now with an urge to test your abilities :30:

Lol, the answer was pitched at the level of the question. As you rightfully point out it's not going to win any science awards but understanding electrical theory has to start somewhere. This was the kind of explanation that's been taught to apprentices including myself for decades so It's a good place to start. We all believed in Santa then in later years were told it was a lie then we learn that even by looking for him we could change the fact he did or didn't exist

 

[Thefailsafe2012]

Lol, the answer was pitched at the level of the question. As you rightfully point out it's not going to win any science awards but understanding electrical theory has to start somewhere. This was the kind of explanation that's been taught to apprentices including myself for decades so It's a good place to start. We all believed in Santa then in later years were told it was a lie then we learn that even by looking for him we could change the fact he did or didn't exist

You mean he's not real? :sad:

 

[FAA Greenie]

An Amp is an Amp, is an Amp, regardless of what's pushing it, or pulling it. Think about high voltage transmission lines and the amount of power that they are able to deliver...

 

[plugsandsparks]

arrrr but what speed does that electron manage as its whizzing its way down the cable?

I remember asking this question at school when we were doing O level physics, even though i had to "go with it" for the exams, i really could not see one electron bothering to make its way all the way from Drax power station to my house.

never made sense to me.

 

[sparky351355]

300,000m/s

 

[FAA Greenie]

Well if you really want to get into it, a single electron doesn't have to move along much of the conductor at all, it only has to dislodge another electron from it's neighbouring atom and take it's place. It can then stay in it's new home forever if it's lucky !!!

 

[Darkwood]

In Ac circuits the electrons vibrate pretty much around their own original position so no actual electron migration and in DC the electrons move so slow it make a snail look fast ....... look up 'speed of electricity' on Wiki and learn why everything you are taught is dumbed down and a lie just to make sure you dont get brain overload ..... classical physics is all you need to know .... advanced physics first rule is forget all the crap you were ever taught.

@sparky 351335 .... 300,000m/s is the speed of the propagation of the EMF not the electrons whizzing around as your answer implies if your going to google it make sure you understand what you read..

 

[Silly Sausage]

I've got a half baked theory on the transmission of electrical energy based on entropy.
But I really need to go to bed, so I'll leave it for another day!

 

[Tridentsystems]

Electrons are almost theoretical anyway as they are never where you look for them. Bit like my hand kit when plumbers are around

 

[Darkwood]

Electrons are almost theoretical anyway as they are never where you look for them. Bit like my hand kit when plumbers are around

Not sure how something can be 'almost' theoretical either way i believe you are mis-interpreting German physician Werner Heisenberg's Uncertainty Principle where using your Electron example you cannot know both its speed and position at the same time but they can be independently measured...

For many years now we have been able to see electrons by using lasers which take a snapshot so fast its measured in the atto-second scale which is needed due to the speed of say an electron you want to look at on say an Hydrogen atom.
In 2010 Electrons were seen for the first time moving in the outer shell of an Atom in real time.... so you have a little catching up to do

 

[D Skelton]

in DC the electrons move so slow it make a snail look fast

About walking pace. Stephen Fry said it so it must be true!

 

[Darkwood]

About walking pace. Stephen Fry said it so it must be true!

He's quite the intellectual in real life and is full of useless well researched facts.. Quite Interesting i find.

 

[D Skelton]

'Thou shalt not question Stephen Fry' - Wasn't that like the 11th commandment or something?! Lol

 

[shanky887614]

In Ac circuits the electrons vibrate pretty much around their own original position so no actual electron migration and in DC the electrons move so slow it make a snail look fast ....... look up 'speed of electricity' on Wiki and learn why everything you are taught is dumbed down and a lie just to make sure you dont get brain overload ..... classical physics is all you need to know .... advanced physics first rule is forget all the crap you were ever taught.

@sparky 351335 .... 300,000m/s is the speed of the propagation of the EMF not the electrons whizzing around as your answer implies if your going to google it make sure you understand what you read..

Simplist way to explain it.

Get a tube 5m long and fill with marbles. As you push one more in from one end another pops out the other but the ones inbetween move incredably slowly

 

[Darkwood]

Depends who your trying to explain this to shanky your explanation works to explain the speed concept but has the confusing angle of making one think the electrons (marbles) are delivering the energy but when you do this concept with AC you have no NET migration so yes it may satisfy the those who just need a visualisation of how it works but this is again a false concept to simplify the workings of the quantum realm.... ive studied quantum theory for 30yrs and it still screws my mind up because its a world that dosn't follow the rules of the Macro world so trying to convey it to someone who only know the real world is practically impossible....

 

[shanky887614]

Depends who your trying to explain this to shanky your explanation works to explain the speed concept but has the confusing angle of making one think the electrons (marbles) are delivering the energy but when you do this concept with AC you have no NET migration so yes it may satisfy the those who just need a visualisation of how it works but this is again a false concept to simplify the workings of the quantum realm.... ive studied quantum theory for 30yrs and it still screws my mind up because its a world that dosn't follow the rules of the Macro world so trying to convey it to someone who only know the real world is practically impossible....

True but its the easiest way to explain how something as slow moving as an electron can have a much larger affect. Quantom physics themselfs are complex because most people try to use known laws that act completely different in reguards to quantom science.

 

[Tiny Spark]

All you need to know is what they tell you in school that electric goes from + to -!

Oh wait...

 

[shanky887614]

All you need to know is what they tell you in school that electric goes from + to -!

Oh wait...

Lol that messes with a lot of peoples minds.

I forget which but electrons flow from pos to neg but electricity from neg to pos

 

[Des 56]

There must be "holes" in these arguments about the flow of electrons

I think its probably best to leave the quantum state to DW
Even with his extensive knowledge,to quote Richard Feyman,
"I think I can safely say no one understands quantum mechanics"

So there we are,there seems little hope of the likes of us getting to grips with this subject,at least not by the end of this thread :blush5:

 

[D Skelton]

What's more, we also know either our current quantum theory or our theory of relativity is wrong, maybe even BOTH, so essentially we're all basing our sums on something which is a coin flip at best!

 

[Darkwood]

Its not that its wrong its the quantum equations we have prove very precise and accurate what is wrong with them is unification of different areas of the quantum world namely gravity, we hae well founded and tested equations that can explain differing areas of the quantum world but we dont have one that links them together or TOE (Theory Of Everything).

As we progress and discover more like last years big find (Higgs Boson) the elusive giver of mass and the recent discovery of new exotic particles the links between the various areas are slowly been made.... dark matter should hopefully be detected within the next 5yrs 'IF IT EXISTS!!!'

 

[Gardner]

I would think it would be the same. Heating is a function of current rather than voltage. Now if your cable is exposed verses imbedded in insulation than there would be a difference from smothered heat dissipation.

 

[D Skelton]

But we know a link doesn't exist between wider quantum theory and relativity (the minutely small and the infinitely large) because one of them (at least) is fundamentally wrong, we know this to be the case but the reason we still use both theories is because they fit what we need them for. Christ we still use newtonian theory even though we definitely know that is wrong. Science is about using what you have until you find something better or more suited to your needs.

 

[Darkwood]

We could always follow the bible bashers ... at least every question can be answered the same ... cos God made it that way!

I had 2 bible bashers at my door so i explained im an Athiest .... they ask me why im an atheist to which i replied 'Because god made me this way' .... their faces were a picture lol

 

[Tiny Spark]

Blaggedhead.org

 

[D Skelton]

I live right next to a Jehova's witnesses kingdom hall and used to get them at the door all the time when we first moved in. They always used to introduce themselves to which I'd always reply with one word... 'Dinosaurs!'

They've stopped coming round now

 

[Mr Hehound]

What's more, we also know either our current quantum theory or our theory of relativity is wrong, maybe even BOTH, so essentially we're all basing our sums on something which is a coin flip at best!

This is why physics is so ace. It evolves as we learn more.

I often lament that its a shame the young have to decide what to study before they're really old enough to understand how interesting some subjects are regardless of whether they're hard or mathmatical.

We'd have alot more physicists and engineers and alot less media studies graduates than we have now.

 

[Darkwood]

If i listened to my school Physics teacher i'd be crap at my job.. i saw him 15yrs later and asked him some indepth physics questions and he could't respond and then ask why we were taught that there was only 3 states of matter ... he said that they was the important ones ...i said they only accounted for less than 3% of the states of matter in the universe and he negated to express that almost all matter was composed of a 4th state............

Ive hated dumbed down teaching ever since ........... its Santa clause and the Tooth Fairy for graduate .... SAD!

 

[Mr Hehound]

If i listened to my school Physics teacher i'd be crap at my job.. i saw him 15yrs later and asked him some indepth physics questions and he could't respond and then ask why we were taught that there was only 3 states of matter ... he said that they was the important ones ...i said they only accounted for less than 3% of the states of matter in the universe and he negated to express that almost all matter was composed of a 4th state............

Ive hated dumbed down teaching ever since ........... its Santa clause and the Tooth Fairy for graduate .... SAD!

Gas plasma? What is it you do?

Think the teacher thing varies tbh. Some good some bad. Until university level they're a bit ham strung by limitations of the syllabus they are told to teach I think.

 

[Darkwood]

Yep PLASMA ...

I repair, upgade machines, design control systems for machinery and industrial electrical installations mainly but can backtrck to the simple stuff to fill the day if need be.

I know what your saying with the teacher thing but it still get my rag that they still teach the basics wrong because its easier if they taught the real world of physics it will weed out the not so intelligent and promote those genuinely interested rather than just keeping the pass rate high and filling the country with numpties.

I went in my old school the other day and was shocked to find a large poster on the wall showing the '9' planets of the solar system not the 8 as we know now...pluto was downgraded several yrs ago but the school literature has been changed due to costs... the teacher explained they are now told the books are out of date so i said ok but isn't it sending a confusing message to have the out-dated posters up ...think he got my point

 

[Tiny Spark]

Fully agree darkwood.
Whats the point of having a A* in science and a high pass rate if everything you are taught is wrong?

Ide rather be taught right first time round and not have my head filled with lies and dumbed down stuff.

It only seems like yesterday I was leaving school (11 years ago) but the gaps in knowledge between what I knew at 16 and the young apprentices we take on seem to be huge.

We even had to teach 1 lad how to use a calc so he could attempt his lvl 2 key skills maths exam!!

 

[Darkwood]

They use calculators now!!!! OMG what next virtual holograms to tell them all the answers they don't know:banghead:

 

[Tiny Spark]

Not very well seemingly Darkwood so I wouldn't worry to much....

On the other hand think everyone needs to....

PANIC!!!!

 

[All4One_One4All]

300,000m/s

A little knowledge is dangerous, and you have demonstrated that little knowledge. Each electron moves one place at a time, and there are billions and billions of them all queued up like traffic on a 5-lane motorway start stop traffic jam (except there are millions of lanes above and below and well as to the left and right, and the cars are really floating. One can only move forwards when the car in front has moved, and it can only move when the car in front of it moved.
Unfortunately, humans thought electricity was due to positive things, and it turned out electrons are negative, so just to confuse you further, the cars move backwards, as if in reverse, but don't assume that's the reason they move quite slowly. The analogy falls down here! So next time you look at a torch battery, remember the electrons come out of the -ve terminal and flow round the circuit to the +ve terminal!

 

[Darkwood]

A little knowledge is dangerous, and you have demonstrated that little knowledge. Each electron moves one place at a time, and there are billions and billions of them all queued up like traffic on a 5-lane motorway start stop traffic jam (except there are millions of lanes above and below and well as to the left and right, and the cars are really floating. One can only move forwards when the car in front has moved, and it can only move when the car in front of it moved.
Unfortunately, humans thought electricity was due to positive things, and it turned out electrons are negative, so just to confuse you further, the cars move backwards, as if in reverse, but don't assume that's the reason they move quite slowly. The analogy falls down here! So next time you look at a torch battery, remember the electrons come out of the -ve terminal and flow round the circuit to the +ve terminal!

Thats DC ... AC has no net migration of electrons but the electricity arrives at close to the speed of light just to add more confusion

 

[Silly Sausage]

Or the positive 'holes' migrating from +ve to -ve!

 

[Tiny Spark]

Somehow I think the student has been scared away....

Cant say I blame him LOL

 

[iamgary25]

I'm sure you lot answered my questions on page one lol

interesting reading the rest lol but thought not to get involved haha

Thanks though