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Resistance Propagation of Error

  1. Oct 1, 2006 #1
    We recently did a Resistance in Circuits lab.

    My coded resistances were
    33, 100 and 220.
    The measured resistance was
    33.3, 101.6 and 219

    So we did 3 setups. (Series, Parallel and Combination)

    Series = 351.8 measured ohms
    Parallel = 22.5 measured ohms
    Combinations = 101.5 measured ohms

    The links below are scanned images of my work.


    I am confused on what i am comparing.
    I find the calculated Req with the uncertainty... so I am comparing that to the measured, but i am confused on what to do with the uncertainty.
    I need to find the discrepancy and say if it is signi. or insigni.

    For Parallel i found, 22.5 -22.3 = 0.2 and the error was 0.141
    So its Sig. But the rest confused me.

    I hope someone can help me understand.
    thanks in advance.
  2. jcsd
  3. Oct 1, 2006 #2
    anyone have any ideas?
  4. Oct 2, 2006 #3
    What equations did you use? There would be a couple ways to measure resistance, and a couple ways to find the error. If you used [tex]R = \frac{V}{i}[/tex] or any number of other equations for resistance then you would be able to find the uncertainty with the master rule for uncertainty, which is [tex]\pd q = \sqrt{(\frac{\partial q}{\partial x}\delta x)^2 +... + (\frac{\partial q}{\partial z}\delta z)^2[/tex] for whatever variables you have.

    You could also use standard deviations for uncertainty, which would be my suggestion.
    Last edited: Oct 2, 2006
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