In article , Dan C wrote:
On Wed, 11 May 2005 18:34:30 -0700, stretch wrote:

No the resistance is NOT the same. That is why the current handling
capacity is different. Your meter is not sensitive to small fractions
of an ohm, but the relays he is controlling ARE if the wire is long
enough and the voltage is marginal. You could get a reference book on
wire and it would give you the ohms per thousand feet. It is different
for every gauge of wire. Then calculate the fraction of 1000 feet that
yopu are using to get the total ohms. Remember to measure the total
length, not just what you are adding. Then double it because the
current has to flow both ways, out in one wire and back in another.

I'll agree that (theoretically) there is a small variation in resistance
between bigger/smaller wire. However...... in this application, which has
a very short length, and a small difference in wire gauge, that is NOT the
reason for current handling differences. It is the diameter (gauge) of
the wire that makes that difference.

And the *reason* that makes a difference is that the larger the diameter, the
lower the resistance.

Sheesh.

Just like a larger water pipe can
handle more flow. Same thing. Only so many electrons can pass through a
given diameter of wire in a given amount of time.

Which is, of course, another way of stating that the *resistance* of a wire
depends on its diameter.

Larger diameter means
more current, and it's not because of any difference in resistance.

Of course it is *exactly* due to the difference in resistance.

--
Regards,
Doug Miller (alphageek at milmac dot com)

Nobody ever left footprints in the sands of time by sitting on his butt.
And who wants to leave buttprints in the sands of time?