Pure silicon contains approximately 1.0 ã— 1016 free electrons per cubic meter. calculate the mean free time ï„ for silicon at room temperature. answer 1.5*10^-12b-your answer in the previous part is much greater than the mean free time for copper given in the textbook. why, then, does pure silicon have such a high resistivity compared to copper? 1-the number of free electrons in copper is much smaller than in pure silicon. thus, the density of free electrons in silicon is larger. a larger density of current carriers means a higher resistivity.2-the number of free electrons in copper is much smaller than in pure silicon. thus, the density of free electrons in silicon is larger. a smaller density of current carriers means a higher resistivity.3-the number of free electrons in copper is much larger than in pure silicon. thus, the density of free electrons in silicon is smaller. a smaller density of current carriers means a higher resistivity.4-the number of free electrons in copper is much larger than in pure silicon. thus, the density of free electrons in silicon is smaller. a larger density of current carriers means a higher resistivity.