3 5 DRIFT OF ELECTRONS AND THE ORIGIN
OF RESISTIVITY
As remarked before, an electron will suffer collisions with the heavy fixed
ions, but after collision, it will emerge with the same speed but in random
directions If we consider all the electrons, their average velocity will be
zero since their directions are random Thus, if there are N electrons and
the velocity of the ith electron (i = 1, 2, 3,