From the picture of the crystal, it is clear that since the spacing of atoms is such that that just “touch” in some sense, the value of ? must be about equal to the lattice spacing between atoms in the crystal, a few tenths nanometer.
From the picture of the crystal, it is clear that since the spacing of atoms is such that that just “touch” in some sense, the value of ? must be about equal to the lattice spacing between atoms in the crystal, a few tenths nanometer.
This all seems pretty reasonable:
- it gives Ohm’s Law
- it gives a resistivity that is too big, but only by an order of magnitude at room temperature, but
- it says that the resistivity should go down as the temperature is increased and the drift velocity increases, not so