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Resistance from I vs. V graph

  1. Feb 15, 2012 #1
    I have a I vs. V graph (I on x-axis, V on y-axis) and I need to figure out how to find the resistance from this.

    I know that R = V/I when the graph is linear, but I have a curved graph...
    I was thinking maybe to sketch a tangent line across each point that I need to figure out its resistance and find the resistance by using ΔV/ΔI.
    Would that be correct?
  2. jcsd
  3. Feb 16, 2012 #2
    Yup , that would be correct. If graph of V vs. I is curve then that means that the conductor is not following ohm's law. That conductor is non-ohmic conductor. Perhaps your method will not give you exact resistance AT THAT POINT but will give you nearest approximation. Yet it will be correct and recommended for beginners. Higher evaluation will involve calculus though.

    Here R=dV/dI or R=ΔV/ΔI at any point.

    http://postimage.org/image/hdqd9a4nl/ [Broken]
    Last edited by a moderator: May 5, 2017
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