Resistivity

R = resistivity = rL/A

Where

r = resistivity (depends on the material

L = length of wire

A = crosss-sectional area of the wire

 

Question:

When you buy extension cords, the longer lengths are typically thicker. Why?

Resistivity at 20 degrees C

There is a temperature dependency but not covered in the course

The resistivity is very strongly affected by small amounts of impurity