Drift of Electrons and the Origin of Resistivity

If the length of a wire conductor is doubled by stretching it while keeping the potential difference constant, by what factor will the drift speed of the electrons change?

Find the resistivity ( in _____$\times {10}^{-6} \mathrm{\Omega m}$) of a conductor which carries a current of density $2.5\times {10}^6 \mathrm{A} {\mathrm{m}}^{-2}$ when an electric field of $15 \mathrm{V} {\mathrm{m}}^{-1}$ is applied across it.

Compare the average drift speed of conduction electrons in a copper wire of cross-sectional area $3.0\times {10}^{-7} {\mathrm{m}}^2$ carrying a current of $5 \mathrm{A}$ with the speed of propagation of electric field along the conductor which causes the drift motion. Assume that each copper atom contributes roughly one conduction electron. The density of copper is $9.0\times {10}^3 \mathrm{kg} {\mathrm{m}}^{-3}$ and its atomic mass is $63.5 \mathrm{u}$.

Compare the average drift speed of conduction electrons in a copper wire of cross-sectional area $3.0\times {10}^{-7} {\mathrm{m}}^2$ carrying a current of $5 \mathrm{A}$ with the thermal speed of copper atoms at ordinary temperatures. Assume that each copper atom contributes roughly one conduction electron. The density of copper is $9.0\times {10}^3 \mathrm{kg} {\mathrm{m}}^{-3}$ and its atomic mass is $63.5 \mathrm{u}$.

The average drift speed of conduction electrons in a copper wire of cross-sectional area $3.0\times {10}^{-7} {\mathrm{m}}^2$ carrying a current of $5 \mathrm{A}$ is $x\times {10}^{-4} \mathrm{m} {\mathrm{s}}^{-1}$. Assume that each copper atom contributes roughly one conduction electron. The density of copper is $9.0\times {10}^3 \mathrm{kg} {\mathrm{m}}^{-3}$ and its atomic mass is $63.5 \mathrm{u}$. Write the value of $x$ to the nearest integer.

(Take $1 e=1.6\times {10}^{-19} \mathrm{C}$ and $N_A=6\times {10}^{23} {\mathrm{mol}}^{-1}$)

If the voltage $V$ applied across a conductor is increased to $2V$, how will the drift velocity of the electron change?