Army Group X Practice Set 1

On stretching, volume V remains constant.
So, V=Al or l=

V

A

Now, R=

ρl

A

=

ρV

A2

=

ρV

π2D4 16

=16ρ

V

π2D4

Taking logarithm of the both sides and differentiating it, we get
Δ

R

R

=−4

ΔD

D

or Δ

R

R

=−4×(−0.25)=1.0%
So, resistance will in crease.