I was looking in my old physics text in connection with another thread and the text said high speed electron collisions and slow speed drift of electrons with an applied electric field don't explain resistivity very well...yielding resistivities 100 times or more than observed. For a plain old resistor, not an exotic semiconductor or such, what's an explanation resistance and associated electrical heating? Also, I noticed tungsten has only 3.3 times the resistivity of copper...so why does it get so hot?? Basically because we make it so thin in filament bulbs??? R = p[l/A]??