3.13 The number density of free electrons in a copper conductor estimated in Example 3.1 is . 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 
and it is carrying a current of 3.0 A. 
                
                  We know,
:Drift Velocity = Length of wire(l) / time taken to cover
 
by substituting the given values
 t = 2.7 x 
 s
Therefore, the time required by an electron to drift from one end of a wire to its other end is   s.