Puzzle

[empip]

Perhaps for the sparkies ...
http://xs315.xs.to/xs315/07195/ResWire-1A.jpg

 

[gcol]

0.063 ohm

 

[Spark123]

10/10 for gcol, now show your working out!!

 

[gcol]

Pt = P0(I + at)
a = temp coeff at 0°C
P50 = 7.6 x 10-6 (I + 0.005 x 50)
= 9.5 x 10-6 ohms per cm3

= (9.5 x 10-6 x 10000)/15

= 0.063 ohm

 

[Spark123]

For some reason I did it the other way around i.e. worked out the resistance per 15cmx1cm cross section, multiplied it by the length (100,000) then applied the temp correction, but arrived at the same answer

 

[gcol]

That sounds like a long winded way of doing it - I prefer just copying the answer down which empip has kindly semi visibly put a link to just above the question.

 

[Spark123]

lol, is it me or should the 10,000 not be 100,000?

I don't think I needed to do the 1/Rx15=1/rt thing, but am happier doing it this way!! I think if you re-arrange the formulae you'll end up with R/15=Rt anyway.

 

[Thermo]

who cares?

 

[Moz]

gcol was around when that ben was flying a kite ...or summat ..lol

 

[gcol]

gcol was around when that ben was flying a kite ...or summat ..lol

How very dare you.

 

[Diyisfun]

You must try & get out more

 

[Moz]

You must try & get out more

what mensa ....
you snobby **nt ????

 

[empip]

lol, is it me or should the 10,000 not be 100,000?

I don't think I needed to do the 1/Rx15=1/rt thing, but am happier doing it this way!! I think if you re-arrange the formulae you'll end up with R/15=Rt anyway.

Yep, 100,000 is correct (text book misprinted model answer).
0.063 Ohm is the biz.

-

 

[bernardgreen]

We had a similar question for A level physics 40 years ago.

The teacher rejected the "correct" answers as we had not considered the ends of the conductor where the cable connected to it. He pointed out that at the ends there would be an area where the current paths were curved towards the point of contact of the conductor rail and feed cable.

He was as always right.