$A$ conductor of length $100 \, cm$ and area of cross-section $1 \, mm^2$ carries a current of $5 \, A$. If the resistivity of the material of the conductor is $3.0 \times 10^{-8} \, \Omega \cdot m$, then the electric field across the conductor is (in $ \, V/m$)

Statement $(I)$: Specific resistance depends on the nature of the material and is independent of the temperature of the material.
Statement $(II)$: $A$ wire of resistance $6 \ \Omega$ is drawn out so that its new length is four times its original length. The resistance of the new wire is $48 \ \Omega$.
Statement $(III)$: Drift velocity is the average constant velocity acquired by free electrons inside a metal by the application of an electric field,which results in current.
Which of the following is correct?

An electric current flows along an insulated strip $PQ$ of a metallic conductor. The current density in the strip varies as shown in the graph. Which one of the following statements could explain this variation?

The area of cross-section of a copper wire is $4 \times 10^{-7} \,m^2$ and the number of free electrons per cubic metre in copper is $8 \times 10^{28}$. If the wire carries a current of $6.4 \,A$,then the drift velocity of the electrons (in $10^{-3} \,m \,s^{-1}$) is:

Electric current is due to the drift of electrons in

$A$ current of $10\, A$ exists in a wire of cross-sectional area of $5\, mm^{2}$ with a drift velocity of $2 \times 10^{-3}\, m/s$. The number of free electrons in each cubic meter of the wire is ..........