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Homework Help: Basic Electricity (what i should know but don't)

  1. Jan 31, 2009 #1
    i have been given this question

    Figure 1 shows a graph of V against I for a filament lamp. Calculate the maximum resistance of the lamp over the range shown by the graph,

    now i have a somewhat vague attempt and its to measure the tangent of the line (i can't upload the graph sorry)

    how do i take a tangent of a curved line accurately and then calculate the maximum resistance

    thank you for your help
  2. jcsd
  3. Jan 31, 2009 #2
    You just need to take a little time and care drawing your tangent.The graph should be steepest at the origin where the resistance is highest..Draw your tangent as long as you can ,construct a right angled triangle where the tangent becomes the hypotenuse and divide the change of voltage by the change of current(tan theta)
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