The drift velocity of the electrons in a copper wire of length $2\ m$ under the application of a potential difference of $200\ V$ is $0.5\ m/s$. Their mobility (in $m^2 V^{-1} s^{-1}$) is

$A$ current $I$ flows through a uniform wire of diameter $d$ when the mean electron drift velocity is $V$. The same current will flow through a wire of diameter $d/2$ made of the same material if the mean drift velocity of the electron is:

Derive the relation between drift velocity and current density.

As shown in the figure,a current is passing through a conducting wire. The radius of the cross-section of the wire at point $A$ is $3r$ and at point $B$ is $r$. Find the ratio of the drift velocity at point $A$ to that at point $B$.

The drift velocity of electrons in a silver wire with a cross-sectional area of $3.14 \times 10^{-6} \, m^2$ carrying a current of $20 \, A$ is. Given the atomic weight of $Ag = 108$ and the density of silver $= 10.5 \times 10^3 \, kg/m^3$,the drift velocity is $.......... \times 10^{-4} \, m/s$.

$A$ charged particle having a drift velocity of $7.5 \times 10^{-4} \, m s^{-1}$ in an electric field of $3 \times 10^{-10} \, V m^{-1}$ has a mobility in $m^{2} V^{-1} s^{-1}$ of: