Physics: Diameter of a nichrome wire
posted by Sar .
If 49 m of nichrome wire is to have a resistance of 13.0 ohms at 20°C, what diameter wire should be used?
I've done this:
(108e8)(49)/10.0 ohms = 5.29e6m^2
Then 5.29e6m^2/pi
then r = sqrt(1.68e6m^2)
and got .00129 = 1.29e3
1.29mm
r=2(1.29mm) = 2.58mm
But this is wrong. Any suggestions?

Where did the 13 ohms go?

Ooo. Gosh, I must have just been looking at the wrong number or something. I feel silly now.

2.27mm is the new answer I got, which is correct. Thanks for pointing that out, Bob. I was going insane trying to figure this out.