7. By considering the number of electrons N travelling a distance I through a conductor (wire) in a time at due to a potential difference between the ends of the conductor, show that the current in the conductor is given by: I = neAv where A is the area of cross-section of the conductor, n is the number of free electrons per unit volume of the conductor, e is the charge on an electron, and Va is the drift speed of the electrons.(4)

Fig: 1