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The resistance of a wire (conductor) in cylindrical form is:

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  1. Jan 21, 2016 #1
    1. The problem statement, all variables and given/known data
    The resistance of a wire (conductor) in cylindrical form is:
    A Disproportional with the length of the wire (conductor)
    B Disproportional with the square of the wire (conductor) section
    C Proportional with the square of the length of the wire (conductor)
    D Proportional with the length of the wire (conductor)

    2. Relevant equations
    R=constant*length/Surface of the section

    3. The attempt at a solution
    I think the answer is D because from the equation of the resistance, but in my book the answer is B
     
  2. jcsd
  3. Jan 21, 2016 #2

    gneill

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    Staff: Mentor

    Assuming that "Disproportional" is a translation of "Inversely proportional", and "section" means the cross section diameter, then both B and D seem to be correct.
     
  4. Jan 21, 2016 #3
    Can you explain me why is B correct?
     
  5. Jan 21, 2016 #4

    gneill

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    Staff: Mentor

    The cross sectional area of a cylinder is proportional to the square of the diameter: ##A = \pi \left( \frac{D}{2} \right)^2##.

    So the resistance should be inversely proportional to ("disproportional" to ) the square of D.
     
  6. Jan 21, 2016 #5
    But it says inversely proportional to the square of section, to the A, not to the diametre.
     
  7. Jan 21, 2016 #6

    gneill

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    Staff: Mentor

    I think it's a matter of a translation issue. I interpreted "section" to be "diameter" rather than "cross sectional area". I could be wrong in this interpretation.

    If "section" means "area" then B is not correct, and only D would make sense.
     
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