Question

A wire of resistivity 'r' is stretched to double its length. How does it affect the (a) resistance (b) resistivity?​

Answer 1

Answer:

resisitivity doesn't change

resistance becomes 4 times

Explanation:

volume=length×area

since no material is added or reduced therefore volume remains same

v=l×a

let new area be a'

v=2l×a'

l×a=2l×a'

a'=a/2

since the material used is same resistivity doesn't change

initial resistance(r)=resistivity(R)×l÷a (resistance =(resistivity×length)÷area)

new resistance(r')=R×2l÷a/2

r'/r=(4×R×l÷a)/R×l÷a

r'/r=4

r'=4r