Hi all, some help needed

[Spark123]

Yes, resistors in series add up, hence if you connect two lengths of cable together you should expect the resistance of the conductors to increase.

Insulation resistance is different as the insulation resistances in a cable act in parallel.

 

[seagullsy]

Yes, resistors in series add up, hence if you connect two lengths of cable together you should expect the resistance of the conductors to increase.

Insulation resistance is different as the insulation resistances in a cable act in parallel.

ah, hang on i think im getting it, the "gray" part of the cable, is the "Insulation resistance"? (the out side part)

now ,by extending a length of cable, the resistance is the same? (for the gray part),

but not for the "circuit conductors",

"circuit conductors" is what i need to be looking into? is this right??

(i think i can only learn in lehmans terms!!!!)

 

[mattylad]

Sounds like your trying to introduce too much into your answer.

your making a cable longer.

The profile of the cable has little to do with the resistance of it's conductors.

If the question does not ask for insulation resistance then do not introduce this into your thinking, just read the question again - say it aloud.

 

[Spark123]

The insulation resistance (IR) is the resistance of the insulation between conductors, wether it be the grey plastic insulation, the brown plastic insulation or the blue plastic insulation as found in the cables.
The insulation is the bit that stops the conductors touching together and shorting out, or someone touching the cable and recieving a shock.

The circuit conductors are the copper bits inside the insulation.

The IR acts in parallel hence if you add to the cable length then the insulation resistance will decrease, think of resistances in parallel where 1/Rt = 1/R1 + 1/R2 + .........

 

[Spark123]

Sounds like your trying to introduce too much into your answer.

your making a cable longer.

The profile of the cable has little to do with the resistance of it's conductors.

If the question does not ask for insulation resistance then do not introduce this into your thinking, just read the question again - say it aloud.

We already answered the original question, just pointing out that the behaviour of the IR of a cable being extended is opposite to that of the circuit conductors.

 

[seagullsy]

right, so it's asking me- if i extend a length of cable, the copper bit in the cable(the circuit conductor,yes??) what will the resistance to (heat im assuming) be? which leads me back to my origanal answer of "stay the same", because weather a cable is 10metres long or 20 meters long, its still the same resistance, no????

 

[Steve]

its the same resistance PER METRE.

More metres = . . . . .

 

[ban-all-sheds]

Resistance to heat???

Seagullsy - I'm not trying to be unkind, but I honestly don't think you've got what it takes to become an electrician.

Learning is one thing, but if you're struggling so badly with something so incredibly basic....

 

[seagullsy]

its the same resistance PER METRE.

More metres = More resistance??

but i dont understand why tho..

 

[oharaf]

I'll give it a whirl..

okay, you are only interested in the length of wire in the cable.

The coating what ever it is has no bearing on this question.

So Think wire.

Right let say we have a length of wire, 10cm to keep the numbers simple!!

We measure the resistance of this piece of wire we find it is 5ohms.



So 10cm of wire has a resistance of 5 ohms.



We get another piece off the drum but this time it is 20cm long.

We measure the resistance and find it is 10ohms



So 20cm of wire has a resistance of 10 ohms.


Q. What do you think will be the resistance of;

(i) 30cm of wire?

(ii) 40cm of wire?

(iii) 35cm of wire?

(iv) What happens to the resistance of wire as it gets longer?[/u][/b]

 

[seagullsy]

I'll give it a whirl..

okay, you are only interested in the length of wire in the cable.

The coating what ever it is has no bearing on this question.

So Think wire.

Right let say we have a length of wire, 10cm to keep the numbers simple!!

We measure the resistance of this piece of wire we find it is 5ohms.



So 10cm of wire has a resistance of 5 ohms.



We get another piece off the drum but this time it is 20cm long.

We measure the resistance and find it is 10ohms



So 20cm of wire has a resistance of 10 ohms.


Q. What do you think will be the resistance of;

(i) 30cm of wire?

(ii) 40cm of wire?

(iii) 35cm of wire?

(iv) What happens to the resistance of wire as it gets longer?[/u][/b]

its that simple??!! oh dear, do i feel like a plum now, thank you so much, i think the problem im having is the way all the books are worded and numbered, i'l get there, wish you were my teacher tho!!! Thanks again, so much.

 

[oharaf]

If only you knew how many times I heard that in the past 12 years!!!

I quit teaching to become an Electrician!!!!!

Let me guess maths and science were not your best subject at school.

Then again the science and maths curriculum are in such a mess now that I am amazed the average 16 year old can even use V=IR.

I was doing this stuff at school when I was 11 years old, and that is only 25 years ago, just wait until you get to conductance and impedance.

Ask your college about maths up date courses, get some GCSE maths and science books (from the 80's) Bostock and Chandler highly reccommended and practice practice practice

 

[seagullsy]

If only you knew how many times I heard that in the past 12 years!!!

I quit teaching to become an Electrician!!!!!

Let me guess maths and science were not your best subject at school.

Then again the science and maths curriculum are in such a mess now that I am amazed the average 16 year old can even use V=IR.

I was doing this stuff at school when I was 11 years old, and that is only 25 years ago, just wait until you get to conductance and impedance.

Ask your college about maths up date courses, get some GCSE maths and science books (from the 80's) Bostock and Chandler highly reccommended and practice practice practice

Thanks pal, your so right! i left school at 14 and am now 30, maths? not a clue. science? i like starwars if that counts. as for V=IR, you wot????!!!!

 

[oharaf]

Oh well at least you're giving it a go, well done.

Get that maths help, can't remember the scheme college will know and it should be free.

The only thing to take from Star Wars is the fact that Strip light tube DO NOT actually make good weapons