By increasing the temperature,the specific resistance of a conductor and a semiconductor respectively

The resistance of a platinum wire at $0^{\circ}C$ is $2\,\Omega$ and $6.8\,\Omega$ at $80^{\circ}C$. The temperature coefficient of resistance of the wire is:

When the temperature of a wire is increased from $303 \ K$ to $356 \ K$,the resistance of the wire increases by $10 \%$. The temperature coefficient of resistance of the material of the wire is:

$A$ metal rod of length $10 \text{ cm}$ and a rectangular cross-section of $1 \text{ cm} \times 0.5 \text{ cm}$ is connected to a battery across opposite faces. The resistance will be . . . . . . .

$A$ hollow cylindrical conductor has a length of $3.14 \, m$, while its inner and outer diameters are $4 \, mm$ and $8 \, mm$ respectively. The resistance of the conductor is $n \times 10^{-3} \, \Omega$. If the resistivity of the material is $2.4 \times 10^{-8} \, \Omega \, m$, the value of $n$ is $..........$

There are two wires of the same length and of the same material and radii $r$ and $2r$. The ratio of their specific resistance is