Question

A wire of resistivity 'r' is stretched to double its length. How does it affect resistance and resistivity

Answer 1

resistivity is directly proportional to wire Resistance and inversely proportional to its length so if length of wire becomes double the resistance also becomes double and resistivity becomes half

Answer 2

When wire is doubled over itself, area is doubled and length is halved.

Resistance is proportional to Length and inversaly proportional to Area.

So

R` = R(1/2)/2

R'=R/4

Resistivity doesn't depend on shape of conductor , so it will remain same