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- PHY102 Physics II © Dr.Cem Özdoğan
- The assumption that the conduction electrons in a metal are free to move like the molecules in a gas leads to an expression for the resistivity of a metal:
- Here n is the number of free electrons per unit volume and τ is the mean time between the collisions of an electron with the atoms of the metal.
- Metals obey Ohm’s law because the mean free time τ is approximately independent of the magnitude E of any electric field applied to a metal.
- The gray lines show an electron moving from A to B, making six collisions in route.
- The green lines show what the electron’s path might be in the presence of an applied electric field E.
- Note the steady drift in the direction of -E.
- 26-6 A Microscopiv view of Ohm’s Law