Do the electrical characteristics of an incandescent bulbs change significantly over its life?
No. In general, the electrical characteristics of tungsten filament bulbs [incandescent and halogen] do not change significantly over their life. However, as the bulb burns, tungsten evaporates and hot spots develop along the filament. This has the effect of slightly increasing filament resistance. At constant voltage, the bulb current will decrease slightly over time. The magnitude of change depends on the bulb design but is on the order of a few percent. Halogen lamps are slightly more stable than incandescent bulbs over their life. The “halogen cycle” captures the evaporated tungsten that burns off of the filament and re-deposits it on the filament surface. The result is that the electrical characteristics of the bulb – including the bulb current – change very little over life.
