$A$ 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:

The electric field $E$,current density $J$ and conductivity $\sigma$ of a conductor are related as

$A$ metal has $9 \times 10^{28}$ conduction electrons per $m^3$ and its resistivity is $1 \times 10^{-8} \Omega \cdot m$. If the drift speed of an electron in the metal is $1.6 \times 10^6 \ m/s$, then its mean free path is (mass of electron $= 9 \times 10^{-31} \ kg$ and charge of electron $= 1.6 \times 10^{-19} \ C$). (in $nm$)

When there is an electric current through a conducting wire along its length,then an electric field must exist

$A$ wire has a non-uniform cross-section as shown in the figure. $A$ steady current flows through it. The drift speed of electrons at points $P$ and $Q$ is $v_P$ and $v_Q$ respectively.

In a copper wire,each atom releases one free electron. If the diameter is $1\, mm$ and the current is $1.1\, A$,find the drift velocity. (Given: Density $\rho = 9 \times 10^{3}\, kg/m^3$,Molar mass $M = 63\, g/mol$,Avogadro number $N_A = 6.023 \times 10^{23}\, mol^{-1}$,Elementary charge $e = 1.6 \times 10^{-19}\, C$)