Number density of free electrons in a copper conductor, `n = 8.5 xx 10^(28) m^(-3)` Length of the copper wire, `l = 3.0` m
Area of cross-section of the wire, `A = 2.0 xx 10^(-6) m^(2)`
Current carried by the wire, `I = 3.0A`, which is given by the relation,
`I = nAeV_(d)`
where,
e = Electric charge `= 1.6 xx 10^(-19)C`
`V_(d) = "Drift velocity" = ("Length of the wire" (l))/("Time taken to cover" (t))`
`I = nAe(l)/(t)`
`t = (nAel)/(I)`
`= (3 xx 8.5 xx 10^(28) xx 2xx 10^(-6) xx 1.6 xx 10^(-19))/(3.0)`
`= 2.7 xx 10^(2)s`
Therefore, the time taken by an electron to drift from one end of the wire to the other is `2.7 xx 10^(4)s`.