This preview shows page 1. Sign up to view the full content.
Unformatted text preview: Chapt. 27 Currents and Resistance 209 3. The probability of electron collision (with an ion, impurity, or defect) in a metal happening in the time span from last collision to time t is P ( t ) = 1 e t/ where is the efolding time for collisions. a) Take the derivative of P ( t ) with respect to time. b) The derivative from part (a) is a probability density for collisions: i.e., dt is the probability for a collision happening in the differential time interval dt . The time interval over which the density applies is from time 0 (immediately after the last collision) to time infinity. If you have N electron flights between collisions, Ndt is the mean number of them that end in dt . Say you have a quantity Q associated with the electron flights: in general Q depends on t . The mean total value of Q for flights that end in dt is QN ( t ) dt . The mean total value for all N flights is N integraldisplay Qdt ....
View
Full
Document
 Fall '06
 Buchler
 Physics, Current, Resistance

Click to edit the document details