Current is flowing with a current density $J = 480\,\,{\rm{A}}\,{\rm{c}}{{\rm{m}}^{ - 2}}$ in a copper wire. Assuming that each copper atom contributes one free electron and given that <br> Avogadro number $ = 6.0\,\, \times \,\,{10^{23}}\,\,{\rm{atoms}}\,\,{\rm{mo}}{{\rm{l}}^{ - 1}}$ <br> Density of copper$ = \,\,9.0\,{\rm{g}}\,\,{\rm{c}}{{\rm{m}}^{ - 3}}$ <br> Atomic weight of copper ${\rm{ = }}\,{\rm{64}}\,{\rm{g}}\,\,{\rm{mo}}{{\rm{l}}^{ - 1}}$ <br> The drift velocity of electrons is