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

[prishila]

Homework Statement

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)

Homework Equations

R=constant*length/Surface of the section

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

 

[gneill]

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.

 

[prishila]

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.

Can you explain me why is B correct?

 

[gneill]

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.

 

[prishila]

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.

But it says inversely proportional to the square of section, to the A, not to the diametre.

 

[gneill]

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.