Resistivity of tungsten filament

  • Thread starter rinarez7
  • Start date
  • #1
27
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]1. A 1.3 cm length of tungsten filament in a small lightbulb has a resistance of 0.032 ohms. Find its diameter.
Given: Length= 1.3 cm= .013m
R= 0.032 ohms
resistivity= 5.6e-8 ohms*meter



2.
A= pi (r^2)
R= resistivity (Length/ Area)



The Attempt at a Solution


R= resistivity ( Length/ pi* (r^2) )
.032 ohms= (5.6e-8 ohms*meter) * (.o13m/ (pi* (r^2)) )
.032 (pi) (r^2) = 7.28e-10
.100530965 (r^2) = 7.28e-10
r= 8.509e-5
diameter= 2r= 1.701e-4m

It asks for the answer in mm, so I divided my answer by 1000= 1.7 e-7 mm, but it's not correct = (
What am I missing?
Thanks in advance!
 

Answers and Replies

  • #2
220
0
1m=1000mm...
 
  • #3
27
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wow do I feel silly! = / thanks
 
  • #4
220
0
wow do I feel silly! = / thanks

Those things happen to everybody from time to time! :biggrin: And you're welcome!
 

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