$A$ metal wire of length $L$ and radius $r$ has a resistance $R$. If a wire of the same metal of length $2L$ and radius $3r$ is taken,then what will be its resistance?

$A$ wire of resistance $x \ \Omega$ is drawn out,so that its length is increased to twice its original length,and its new resistance becomes $20 \ \Omega$. Then $x$ will be ........ $\Omega$.

Resistance of a wire at $0^{\circ} C, 100^{\circ} C$ and $t^{\circ} C$ is found to be $10 \Omega, 10.2 \Omega$ and $10.95 \Omega$ respectively. The temperature $t$ in Kelvin scale is $\qquad$

The resistivity of a material is found to be $10^8 \Omega \cdot m$. Then the material would be

As shown in the schematic below,a rod of uniform cross-sectional area $A$ and length $l$ is carrying a constant current $i$ through it and the voltage across the rod is measured using an ideal voltmeter. The rod is stretched by the application of a force $F$. Which of the following graphs would show the variation in the voltage across the rod as a function of the strain $\varepsilon$ when the strain is small? Neglect Joule heating.

The dimension of $\sqrt{\frac{\mu_0}{\epsilon_0}}$ is equal to that of (where $\mu_0 = \text{vacuum permeability}$ and $\epsilon_0 = \text{vacuum permittivity}$)