I think the ribbon corresponds to a 21 gauge wire because
.126 x .005 yeilds .00063 sq in, corresponding to 28.3 mils
diameter...same as 21 gauge. So, according to the table at
http://www.wiretron.com/nicrdat.html
it ought to have .80 to .83 Ohms per ft., depending on
composition. So, 3.5 inches should do it. However,
you plan to put about 40 Amps through it and the other
chart on the page say that 14.8 Amps will cause the wire
to operate at 2000 deg F. It will make a nice flash at
40 Amps.
As an aside, the whole 29 inches operating at 14.8 Amps
will dissapate about 400 W and run at 2000F.
jeff
----- Original Message -----
From: "Phil Levin W2GE" <w2ge@home.com>
To: <amps@contesting.com>
Sent: Thursday, October 19, 2000 10:14 PM
Subject: [AMPS] Nichrome wire resistance?
>
> I was able to get a hold of a 29" long piece of "Nichrome ribbon", I am
not
> sure of it's exact alloy make-up, I was just told its Nichrome. It
measures
> 3.19 mm (0.126 inches) in width and its .17 mm in thickness (0.005 inches)
> as measured on an electronic digital caliper (new toy I just got, thrilled
> with it, BTW...forgive me for going OT, Tool Nerd here!) I'm having
trouble
> measuring this low of a resistance, does anyone know from a chart what
> resistance I should expect from this wire? I'm looking for approx .24
ohm.
> (Jeff M. got an answer for me?) Thanks all. Phil W2GE
>
>
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