At room temperature,copper has a free electron density of $8.4 \times 10^{28} \, m^{-3}$. The copper conductor has a cross-section of $10^{-6} \, m^2$ and carries a current of $5.4 \, A$. The electron drift velocity in copper is:

Though the electron drift velocity is small and electron charge is very small, a conductor can carry an appreciably large current because

$A$ potential difference of $5 \,V$ is applied across a conductor of length $10 \,cm$. If the drift velocity of electrons is $2.5 \times 10^{-4} \,m/s$,then the electron mobility will be ............ $m^2 V^{-1} s^{-1}$.

Consider a conductor of length $40 \ cm$,where a potential difference of $10 \ V$ is maintained between the ends of the conductor. Find out the mobility of the electrons,provided the drift velocity of the electrons is $5 \times 10^{-6} \ m/s$.

Two identical conductors are kept at the same temperature. If the ratio of the potential difference across them is $1 : 2$,what will be the ratio of their drift velocities?

$(a)$ Estimate the average drift speed of conduction electrons in a copper wire of cross-sectional area $1.0 \times 10^{-7} \; m^{2}$ carrying a current of $1.5 \; A$. Assume that each copper atom contributes roughly one conduction electron. The density of copper is $9.0 \times 10^{3} \; kg/m^{3}$ and its atomic mass is $63.5 \; u$.
$(b)$ Compare the drift speed obtained above with,$(i)$ thermal speeds of copper atoms at ordinary temperatures,$(ii)$ speed of propagation of electric field along the conductor which causes the drift motion.