The resistivity of a wire depends on its

The length of a given cylindrical wire is increased by $100\,\%$. Due to the consequent decrease in diameter,the percentage change in the resistance of the wire will be ................ $\%$.

If a conducting wire of length $L$ is uniformly stretched to double its length, then its conductivity becomes . . . . . . .

$A$ wire of circular cross-section has an inner portion of radius $R$ made of a material of resistivity $\rho$ and is surrounded by an outer portion of thickness $R$ made of a material of double resistivity. Find the resistance of a length $l$ of such a wire.

Two wires of equal diameters,of resistivities $\rho_1$ and $\rho_2$ and lengths $l_1$ and $l_2$,respectively,are joined in series. The equivalent resistivity of the combination is

The resistance of a bulb filament is $100\,\Omega$ at a temperature of $100\,^{\circ}C$. If its temperature coefficient of resistance is $0.005\,^{\circ}C^{-1}$,at what temperature will its resistance become $200\,\Omega$?