Key Points!
- Resistance is caused by scattering due to
temperature and imperfection
- Drift is a small perturbation of random walk due
to an electric field (kT is much larger then q grad(E)). Lead to Ohms
law!
- Definition of mobility and conductivity of a
carrier.
- Diffusion is flow due to the concentration
gradient.
- Definition of Diffusivity
Questions
- What causes resistance in a material? How does
temperature effect the resistance of metal? a semiconductor?
- What is the resistance of perfect material at 0K?
- What is a drift current? What are the equations we
use to describe it (define it in terms of conductivity).
- What is the macroscopic version of drift current.
- What is the diffusion of electrons?