Then the average “drift” velocity of a random electron, making a collision after the average time ? is We can express ? in terms of the mean free path and the average electron velocity:

• Then the average “drift” velocity of a random electron, making a collision after the average time ? is We can express ? in terms of the mean free path and the average electron velocity:

and can get the average velocity from the thermal velocity with the thermal kinetic energy, for three degrees of freedom (xyz) this is 3/2(kT), so

and it is striking that this average velocity is typically 1010 times vd, so the average is not affected by E

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