What is the resistivity of a perfect conductor?

Resistance of a wire is $8 \Omega$. It is drawn in such a way that it experiences a longitudinal strain of $400 \%$. The final resistance of the wire is (in $Omega$)

$A$ copper wire is stretched to increase its length by $0.1\%$. What is the percentage increase in the resistance of the wire (in $\%$)?

The specific resistance of all metals is most affected by

$I-V$ characteristic of a copper wire of length $L$ and area of cross-section $A$ is shown in the figure. The slope of the curve becomes

Two wires of equal diameters,lengths $l_1, l_2$ and having resistivities $S_1, S_2$ respectively are joined in series. The equivalent resistivity of the combination is