The number density of free electrons in a copper conductor estimated in Example 3.1 is 8.5 × 1028 m−3. How long does an electron take to drift from one end of a wire 3.0 m long to its other end? The area of cross-section of the wire is 2.0 × 10−6 m2 and it is carrying a current of 3.0 A.
Number density of free electrons in a copper conductor, n = 8.5 × 1028 m−3 Length of the copper wire, l= 3.0 m
Area of cross-section of the wire, A = 2.0 × 10−6 m2
Current carried by the wire, I = 3.0 A, which is given by the relation,
I = nAeVd
e = Electric charge = 1.6 × 10−19 C
Vd = Drift velocity=`"Length of the wire (l)"/"Time taken to cover l(t)"`
Therefore, the time taken by an electron to drift from one end of the wire to the other is 2.7 × 104 s.