$A$ resistance $R$ is stretched to four times its length. Its new resistance will be

$A$ wire of resistance $R$ is stretched until its radius is halved. What will be the new resistance (in $, R$)?

Describe the effect of temperature on the electrical resistance of metals and semiconductors.

The graph showing the variation of resistance $(R)$ of a metal wire as a function of its diameter $(D)$,while keeping other parameters like length and temperature constant,is:

$A$ uniform metal wire carries a current of $2 \, A$ when an ideal cell of $3.4 \, V$ is connected across it. The wire has mass $8.92 \times 10^{-3} \, kg$, density $8.92 \times 10^3 \, kg/m^3$ and resistivity $1.7 \times 10^{-8} \, \Omega m$. Then the length of the wire is (in $m$)

Equal potentials are applied on an iron and copper wire of the same length. In order to have the same current flow in the two wires, the ratio $r_{\text{iron}} / r_{\text{copper}}$ of their radii must be (Given that specific resistance of iron = $1.0 \times 10^{-7} \, \Omega \cdot \text{m}$ and specific resistance of copper = $1.7 \times 10^{-8} \, \Omega \cdot \text{m}$)