# Physics: Diameter of a nichrome wire

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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:
(108e-8)(49)/10.0 ohms = 5.29e-6m^2
Then 5.29e-6m^2/pi
then r = sqrt(1.68e-6m^2)
and got .00129 = 1.29e-3
1.29mm
r=2(1.29mm) = 2.58mm

But this is wrong. Any suggestions?

• Physics: Diameter of a nichrome wire -

Where did the 13 ohms go?

• Physics: Diameter of a nichrome wire -

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

• Physics: Diameter of a nichrome wire -

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.

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