Which of the following is the unit of mobility of an electron in a conductor?

The current density in a cylindrical wire of radius $r = 4.0 \, mm$ is $J = 1.0 \times 10^{6} \, A/m^{2}$. The current through the outer portion of the wire between radial distances $r/2$ and $r$ is $x \pi \, A$,where $x$ is ..........

In a metallic conductor,under the effect of an applied electric field,the free electrons of the conductor

Drift velocity $V_d$ varies with the intensity of electric field $E$ as per the relation:

The $SI$ unit of the current density is . . . . . . .

The number density of free electrons in copper is nearly $8 \times 10^{28} \ m^{-3}$. $A$ copper wire has an area of cross-section $= 2 \times 10^{-6} \ m^2$ and is carrying a current of $3.2 \ A$. The drift speed of the electrons is $..... \times 10^{-6} \ m \ s^{-1}$.