CHEM 212 Lecture Notes - Lecture 3: Joule Heating, Voltage Source, Drift Velocity
Document Summary
Positive charge on anode + negative charge on cathode. Transforms one type of energy into electrical energy (v) battery + rotor. In conductors, valence e are free once electric field is applied, e will move in opposite direction of field. I=delta q/delta t (si units of i: c/s or a) Current direction: defined by direction of positive charge (or more precisely, effective positive charges) When e=0: due to collisions, direction is random -> no net movement. When e-field is applied: free e drift in direction opposite to e-field w/small avg velocities. Charge passing by observation point in t sec: q=nea x=neav t. Charge passing observation point: i=deltaq/deltat=nevat/t=neva: n depends on material. Larger potential difference across material, larger current -> v=ir. Potential drop across resistor: v=el: j=i//a (density, j= e ; conductivity -> Resistivity and conductivity p=1/ ; p=resistivity (incorporate into r eqn)
