$A$ conducting wire has length $L_1$ and diameter $d_1$. After stretching,the same wire's length becomes $L_2$ and diameter $d_2$. The ratio of resistance before and after stretching is:

Arrange the following materials in increasing order of their resistivity: Nichrome,Copper,Germanium,Silicon.

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 = $1.7 \times 10^{-8} \, \Omega \cdot \text{m}$)

For a metallic wire,the ratio of voltage to corresponding current is

The current flowing through a conductor connected across a source is $2\,A$ and $1.2\,A$ at $0^{\circ}C$ and $100^{\circ}C$ respectively. The current flowing through the conductor at $50^{\circ}C$ will be $......\times 10^2\,mA$.

$A$ cell of $emf$ $E$ and internal resistance $r$ is connected across an external resistance $R$. Plot a graph showing the variation of potential difference $(V)$ across $R$ versus $R$.