# Why do only thick wires have less resistance?

I have learned that the thicker a wire is, the less resistance it has. However, this is not the case for other things such as a wall. If a (non-metal) wall is thicker it does not have a lower resistance. Why is this? Thanks in advance.

• Thank you both for the answers. I am new to this community and am already loving it!!! – l33tcookiemonster Dec 9 '14 at 3:38
• Insulators do not obey the rules of conductors. – Dale Mar 25 '18 at 18:39

Resistance in a wire can be defined as

$$R = \frac{\rho L}{A}$$

where

$\rho$ = resistivity

$L$ = Length

$A$ = cross sectional area

Thicker gauge wires have a larger A, and therefore the resistance of the wire decreases keeping everything else constant.

If you are asking about non metallic objects, than they might not be conductive (very high $\rho$), and so their resistance would be extremely high. If the object is conductive, then the $\rho$ of that material would play a factor in its overall resistance.

Below is an image that shows the resistivityof various types of meterial. Rubber is not considered to be conductive and look at its resistivity compared to copper which is conductive.

Source for image

Because it's not the thickness of the object, it's the thickness of the electrical path. A thicker wall does not increase the thickness of the path but instead increases its length, thereby increasing resistance.

How much electrical resistance does ANY wall have? Think of the wall as a very short and very fat conductor. It happens to have VERY high resistivity, so its resistance will be very high, but if you double the size of the wall, its resistance will be halved. Maybe still very large but halved.

So, your question is somewhat confused, because you are comparing two materials (metal in a wire and a wall that does not conduct much, at all) that are grossly different. So different that the material difference totally obscures the question about conductor cross-section.