Given, Initial resistance of wire be R, Initial length of wire be l, Final resistance of wire be R′ and final length of wire be l′. ∵R=
ρl
A
where, R is resistance, l is length, ρ is resistivity and A is area of cross-section. As we know that, on stretching wire, volume remains the same. ∴ Change in volume, ∆V= constant ⇒Area(A)× Length (l)= constant By using percentage error calculation,