$A$ wire of resistance $R$ is elongated $n$-fold to make a new uniform wire. What is the resistance of the new wire?

$A$ negligibly small current is passed through a wire of length $15 \; m$ and uniform cross-section $6.0 \times 10^{-7} \; m^{2},$ and its resistance is measured to be $5.0 \; \Omega .$ What is the resistivity of the material at the temperature of the experiment?

The length and area of cross-section of a copper wire are respectively $30 \ m$ and $6 \times 10^{-7} \ m^2$. If the resistivity of copper is $1.7 \times 10^{-8} \ \Omega \ m$,then the resistance of the wire is (in $\Omega$)

If a wire of resistance $R$ is melted and recasted to half of its length,then the new resistance of the wire will be

The resistance of a coil is $4.2\, \Omega$ at $100\,^{\circ}C$ and the temperature coefficient of resistance of its material is $0.004\,^{\circ}C^{-1}$. Its resistance at $0\,^{\circ}C$ is ............. $\Omega$.

$A$ piece of copper is to be shaped into a conducting wire of maximum resistance. If the initial length is $L$ and diameter is $d$,what should be the new length and diameter to achieve maximum resistance?