Find the resistance of a wire (conductor)

[prishila]

Homework Statement

If the diameter of a wire (conductor) is dimidiated , then its resistance:
A Remains unchangable
B is diminiated
C Becomes two times greater
D Becomes 4 times greater

Homework Equations

R=constant*length/Surface

The Attempt at a Solution

Cross sectional area=pi r^2=pi (D/2)^2=piD^2/4
Then the resistance becomes 4 times greater.
But in my book the answer is C.

 

[Dr. Courtney]

Is the surface area really proportional to r^2?

 

[prishila]

Is the surface area really proportional to r^2?

I think it is. Only if you consider pi to affect that

 

[Dr. Courtney]

Are you confusing surface area and cross sectional area?

 

[prishila]

Are you confusing surface area and cross sectional area?

Can you tell me the difference. in my book it says Resistance is in disproportional to the cross section of the resistance.

 

[cnh1995]

Can you tell me the difference. in my book it says Resistance is in disproportional to the cross section of the resistance.

Surface area means area of the entire surface of the conductor. Cross sectional area is the area "through" which the current flows. Resistance is inversely proportional to the cross sectional area of the conductor.

 

[prishila]

Surface area means area of the entire surface of the conductor. Cross sectional area is the area "through" which the current flows. Resistance is inversely proportional to the cross sectional area of the conductor.

I understand. But how can this affect the solution of my exercise?

 

[haruspex]

I understand. But how can this affect the solution of my exercise?

If "dimidiated" means halved, I agree that the answer is D.