resistance of various metals

[Chris W]

I have seen charts that show how the resistance of various metals
compare. What I haven't seen is a way to make determine how much larger
say a stainless steel rod would need to be to have the same resistance
as a copper rod of some given diameter. For example if I had a 30 awg
copper wire and a 1" dia Stainless steel rod, even though the copper is
a better conductor, in this case the 1" dia stainless steel rod is going
to have less resistance. Is there a rule of thumb, or chart that tells
how much larger to make a conductor to have equivalent resistance to copper?


--
Chris W
KE5GIX

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[Phil Allison]

"Chris W"

I have seen charts that show how the resistance of various metals compare.
What I haven't seen is a way to make determine how much larger say a
stainless steel rod would need to be to have the same resistance as a
copper rod of some given diameter. For example if I had a 30 awg copper
wire and a 1" dia Stainless steel rod, even though the copper is a better
conductor, in this case the 1" dia stainless steel rod is going to have
less resistance. Is there a rule of thumb, or chart that tells how much
larger to make a conductor to have equivalent resistance to copper?

** Are you for real ????

Got no idea that a wire's or rod's resistance is * inversely proportional *
to its cross sectional area ?

Ever figure out that two similar wires run in parallel have half the
resistance of one ???

Chris W
KE5GIX

** A real dope -

even by the most humble standards of ham operators.



........ Phil

 

[Al Forster]

"Chris W" wrote in message news:20vwj.5938$yk5.2981@newsfe18.lga...

I have seen charts that show how the resistance of various metals
compare. What I haven't seen is a way to make determine how much
larger say a stainless steel rod would need to be to have the same
resistance as a copper rod of some given diameter. For example if I
had a 30 awg copper wire and a 1" dia Stainless steel rod, even
though the copper is a better conductor, in this case the 1" dia
stainless steel rod is going to have less resistance. Is there a
rule of thumb, or chart that tells how much larger to make a
conductor to have equivalent resistance to copper?

No chart that I'm aware of, but not difficult to calculate. Find a
table of resistivities for metals eg
http://en.wikipedia.org/wiki/Electrical_resistivity#Table_of_resistivitiesand calculate fromResistance = (resistivity * length) / x-sectional area.Hope this helpsAl

 

[Don Klipstein]

In <47c28d96$0$3161$c30e37c6@pit-reader.telstra.net>, Al Forster wrote:

No chart that I'm aware of, but not difficult to calculate. Find a
table of resistivities for metals eg
http://en.wikipedia.org/wiki/Electrical_resistivity
#Table_of_resistivities

You will have to look up or determine the resistivity of your specific
stainless steel - there are a lot of different stainless steels.

- Don Klipstein (don@misty.com)

 

[Chris]

On Feb 25, 3:42 am, "Al Forster" <a.fors...@student.unsw.edu.au>
wrote:

"Chris W"  wrote in messagenews:20vwj.5938$yk5.2981@newsfe18.lga...
I have seen charts that show how the resistance of various metals
compare.  What I haven't seen is a way to make determine how much
larger say a stainless steel rod would need to be to have the same
resistance as a copper rod of some given diameter.  For example if I
had a 30 awg copper wire and a 1" dia Stainless steel rod, even
though the copper is a better conductor, in this case the 1" dia
stainless steel rod is going to have less resistance.  Is there a
rule of thumb, or chart that tells how much larger to make a
conductor to have equivalent resistance to copper?

No chart that I'm aware of, but not difficult to calculate. Find a
table of resistivities for metals eg
 http://en.wikipedia.org/wiki/Electrical_resistivity#Table_of_resistiv....calculate fromResistance = (resistivity * length) / x-sectional area.Hope this helpsAl

Easy to calculate from the equation Al gave. Total resistance is the
same, total length is the same, so if you have a material that's eight
times the resistivity, by the equation it will have to have eight
times the cross-sectional area. Simple algebra.

Which means the resistivity chart the OP is looking at is actually the
chart he needs -- if he has a calculator, he can divide the
resistivity of stainless steel by the resistivity of copper, and that
tells him how many times more cross-sectional area he needs.

And a newbie alert if Chris is doing the calculations to determine
resistance instead of just calculating ratios -- watch your terms.
Charts for resistivity are frequently expressed for CM, circular
mils. One circular mil is the area of a circle 1 mil in diameter.
This is *not* 1 square mil -- you need to convert!

http://en.wikipedia.org/wiki/Circular_mils

Good luck with your studies.
Chris