1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

R through a wire: What's the max error in diameter if your R has 1% uncertainty?

  1. Jan 23, 2013 #1
    1. The problem statement, all variables and given/known data

    I have a wire of some resistance, resistivity, and length.

    What is the maximum error in measuring the diameter that you can have if the resistance is to have 1% uncertainty?


    2. Relevant equations

    R = [itex]\frac{ρ*l}{\pi*r^{2}}[/itex] for which I substituted the area as [itex]\pi[/itex](.5 D) ^{2}.


    3. The attempt at a solution

    I picked an arbitrary R and found the corresponding D. Then, I took 1% of that arbitrary R and found the corresponding D. The issue is that D's were basically the same number. I'm not sure if I could just go out to more decimal places or if I'm just wrong....
     
    Last edited: Jan 24, 2013
  2. jcsd
  3. Jan 24, 2013 #2

    ehild

    User Avatar
    Homework Helper
    Gold Member

    You meant R = [itex]\frac{ρl}{\pi*r^{2}}[/itex] , didn't you?

    Solve the problem symbolically. If the resistance can differ from R by one percent it can be 1.01 R or 0.99 R. What are the corresponding diameters and how are they related to the original D? By what percent are they different from it?


    ehild
     
  4. Jan 24, 2013 #3
    Typo, thank you!

    Big help!!! Turns out I was off by a decimal point. My answer makes a lot more sense now. Thank you very, very much.
     
  5. Jan 24, 2013 #4
    Another clarification-- the D in the denominator is squared. Does that mean I need to take the square root of my result?
     
  6. Jan 24, 2013 #5

    ehild

    User Avatar
    Homework Helper
    Gold Member

    What is your result at all?

    ehild
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: R through a wire: What's the max error in diameter if your R has 1% uncertainty?
  1. What is R (Replies: 3)

Loading...