>
> what causes Incandescent Bulbs to Burn Out & Resistors to Open

Bulbs burn out because tungsten metal evaporates off the hot filament and
deposits elsewhere in the lamp (or back on the filament in a halogen lamp,
but in the wrong place).

Resistors open because they run very hot and have deliberately thin
conductors that eventually oxidize enough at some point to get into an
accelerating loop of higher temperature --> increased oxidation --> higher
temperature at that point.

Yrs,
d