After each collision the direction of the velocity of the electrons is arbitrary, and this initial velocity after collisons drops out of the equations. It depends on the material and on temperature. We can also find the distance traveled between collisions, the mean free path of the electrons. Because the electrons are fermions, the occupy energy levels upto the Fermi energy. A typical speed of an electron can be found from which gives an estimate of the mean free path .
Calculated values are many times larger then the atomic distance.
Electrons are waves and they only scatter from the periodic lattice of atoms when the Bragg condition is met. Therefore the mean free path is larger at lower temperature and in more pure materials. This is observed when we plot conductivity versus temperature for many materials. In the same model we can also analyze the thermal conductivity. The electrical conductivity in one dimension has the form Electrical currents are diven by a potential difference.