Current Density

You want a current density of 5000 Amps per what? You need to know the cross sectional area to know the current density.

If it was 5000 amps per cm^2 then to get the same current density from a tenth of this (500 amps) you will need a conductor one tenth the cross sectional area.

John.

Yup.

I guess it depends on the voltage, but wouldn't this get rather warm in operation?

It would depend on the cross sectional area to which the questioner refers to... which he doesn't say, so it might do, or it might not??

John.

Good point!

Current density -amps per sq.inch or per sq.mm

I think he wants carry 5000 amps from one place to another place through cable.500 amps may be current density per sq inch-

To answer and help the guest we have to guess various assumptions.

First the guests should post correct and reasonable queries.They should reveal their identity.

There should be some filter mechanism to screen the queries.

Of late many questions are posted like this.

Quite correct, I don't wish to be mean minded but:-

I look at the basic question if it looks short of relevant information I don't waste my time pondering all the probability's I pass on to a more deserving case. If the information looks as though the Questioner has tried to cover his points but has got it wrong due to misinformation or lack of knowledge then it is worth considering.

To be honest the above case indicates the person would not have the slightest idea of what to do with any possible number of answers that could be applied to the question

ramvinod writes: "They should reveal their identity."

Why should guests reveal their identity? What value would such information add to a guest's post other than make it possible for the rest of us to distinguish one guest from another?

I myself have submitted over 2,628 posts to date without having had to reveal my identity, nor would it have mattered one whit had I done so. My nom de plume, europium, tells you absolutely nothing about me and contributes nothing to my posts. I may even be this "guest" posting anonymously as far as you know. You really don't know; nor does it matter.

ramvinod writes: "First the guests should post correct and reasonable queries."

And if they don't post such queries? Maybe they don't know their subject matter well enough and are trying to learn more, perhaps? Who are we to demand our guest serve us his/her query on a silver platter?

Look, if we need more information from our guests, ask for it! If our guest asks an ill-formed question, help him/her ask a better question! That's why we're here.

Let us also not forget that they are our guests.

I am not here to argue with any one.

That was my view.

To reveal identy means at least we will know from which part of World the query is raised, so that we can answer carefully and correctly understanding the local regulations etc.

In this instance many contributor has answered and responded but the Guest has not responded and corrected the query

Sorry for not responding before, this is the first time I've been back since I posted the question. I admit my question was asked out of complete ignorance of what I am talking about. I had no idea what current density meant except it is related to wire size somehow. From the answers above I can see my question lacks one ingredient, ie, a cross sectional wire size. But I didn't know that when I asked the question - I thought that was what I was asking the question to find out. Now it seems I need to tell you my reason for asking the question and I am happy to do that - I am reading and trying to understand a paper in which it says that a current supply of up to 100 amps achieves a current density of up to 1000 amps. The writer doesn't mention a cross sectional area element in the statement. Hence my question. But now I also see from your answers that because of the lack of a per cross sectional area element in the writer's statement then it makes my question pointless. Hence your confusion and my ignorance. At least I now know that I need more information which the writer of the paper neglected to impart and I would sincerely like to apologise for the confusion and for your annoyance which I completely understand. Anyway, thanks to your efforts, I'm a little bit further advanced in knowledge than I was before I asked the question so you have helped me. Finally, I would particularly like to mention europium's insight for being able to understand that questions are asked out of ignorance of some aspect and that is the reason for asking a question in the first place. But I also recognise that if I had made my reason for asking clear in the first place then you may not have resented my question for it's lack of knowledge. For that I sincerely apologise.

Anyway, thanks to your efforts, I'm a little bit further advanced in knowledge than I was before

That is what it is all about and please come back any time. Thanks for coming back to let us know the outcome.

Finally, I would particularly like to mention europium's insight for being able to understand that questions are asked out of ignorance of some aspect and that is the reason for asking a question in the first place.

What is a question that is not born from ignorance? A test maybe! We do not like impromptu tests so I feel that your type of questions are the best and it looks like Europium agrees with me. Tests are fine but only if we choose to take them.

But I also recognise that if I had made my reason for asking clear in the first place then you may not have resented my question for it's lack of knowledge. For that I sincerely apologise.

Last from me, don't apologise for that, just learn and come back to show you have done so

And finally, remember that the only dumb question is one that is never asked.

Hi you came back well with an answer to our perturbations and deserve a bit of attention for that.

Your last question does not have the same quantities as the first but they divide out to the same result.

Basically what you are looking for is Current density is a measure of the density of electrical current. It is defined as a vector whose magnitude is the electric current per cross-sectional area. In SI units, the current density is measured in amperes per square meter.

So 100amps through a 1sq/mt cable =CD of 100 amps, to obtain a 1000 amp CD

the cable CSA = 1sq/mt divided by 10 = 0.1 sq/mt.

If you had done a little googling for current densities you would have had enough information to ask your question in a better way

As the others have said Guest, you are one of the rare 'guests' that has come back and acknowledged our responses.

That in itself is worth the slight effort needed to reply to your first question.

For that I thank you.

John.

Reading your reply,

You are only one click and less than second away from over 14,000,000 answers for your question. My mom use to say move your brains before you move your lips.

I say to my sons and (daughters), google before you move your fingers.

See how times change?

Wangito.

Wangito advises: "...google before you move your fingers."

-----

Telepathic interface or something more prosaic?

YOU know what I mean but hey, it would make a very very interesting concept... and an engineering challenge.

Wangito.

I understand Mr Ramvibod's reply is quite reasonable.

Resonance using an AC power supply, a tuned circuit has peak current flow, detuned is minimal current flow.

The size of the copper wire will be determined by the metalurgy of the wire, which will act as a fuse or heating element, the length of time the wire must carry the current, etc.

Household breakers are rated at 10,000 Amps interrupting current, wire gauges would range from 14 to 10 on a 20 amp breaker.

From this I think it is apparnet there are a number of questions:

1. How long do you want the current flow, as the conductor size will decrease as the current carrying time decreases.

2. Is the current source AC or DC?

3. What voltage range are you working with?

CCM I think you should read post #10 where the guest corrects his question.

Ditto.

Pretty unclear question

Current density is expressed by the following

1A/in² or 0,785A/cmil, or 0.155A/cm² (area of Cu conductor @28⁰C.)

You can take it from here if you know what exactly you want. (and I doubt it very much,) 'cuase I don't.

Wangito.

After reading your comments in #10, it is apparent that they are talking about "skin effect" of current flow, the current flows on the outside of the conductor, thus a tube could apparently carry the same curent as a solid conductor.

I think this gets closer to what you are describing.

Coronaman,

In this case wouldn't our poster be much better off at www.bestcrosswords.com and not at CR-4?

I hate cross words on my drafting table...

Wangito

CCM writes: "After reading your comments in #10, it is apparent that they are talking about "skin effect" of current flow, the current flows on the outside of the conductor, thus a tube could apparently carry the same curent as a solid conductor."

Where does Post #10 make it "apparent" that the poster is talking about skin effect? Does the poster say anywhere (anywhere at all?) that he's talking about RF or transient conditions where skin effect would come into play? Please enlighten me if I seemed to have missed something in his posts.

When the current density increases by 10X in a specific volume how else could it be done? I was a Navy radar repair tech also long before slowing down in frequency to electrical power. I have also shown the manufacturer how to use infrared to look at welds on heart pacemaker wires using a current source to determine that the welded area was a good no resistance contact and that the contact area was as great as the conductor.

Listening to Olivia Newton John, asking for body talk, I am distracted but in tune with the discussion.

CCM asks: "When the current density increases by 10X in a specific volume how else could it be done?"

See Post #1.

I think we have reached the proverbial circle of meaningless questions, dog chasing his tail! Nothing useful being discovered, I'm outa here.