The dimensions of resistivity in terms of $M, L, T$ and $Q$,where $Q$ stands for the dimensions of charge,is:

$A$ 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 $..........$

The resistance of a wire at $50^{\circ}C$ is $5\, \Omega$ and at $100^{\circ}C$ is $6\, \Omega$. The resistance of the wire at $0^{\circ}C$ is ............... $\Omega$.

Two metallic wires of identical dimensions are connected in series. If $\sigma_{1}$ and $\sigma_{2}$ are the conductivities of these wires respectively,the effective conductivity of the combination is:

If a copper wire is stretched to make its radius decrease by $0.1\%$,then the percentage increase in resistance is approximately .......... $\%$

$A$ wire of resistance $160\,\Omega$ is melted and drawn into a wire of one-fourth of its original length. The new resistance of the wire will be $......\Omega$.