Why do light bulbs burn out right when you turn them on?


Why do light bulbs burn out right when you turn them on?

In: Technology

The filament (of incandescent bulbs) it’s very very thin wire. Repeated heating and cooling from turning it on and off gradually weakens it, til one time turning it on and rapidly increasing its temperature causes it to snap which is what makes the lightbulb pop.

Assuming you mean the old filament type incandescent lights. The filament gives off light when it heats up. Resistance increases as temperature increases. Current decreases when resistance increases. So when you first turn on the light, when the filament is cold, is when the filament has the lowest resistance and sees the greatest current.

This initial current can be what causes the filament to burn out. In truth it is a bit more complicated – because the degradation over time is not even throughout the filament, so there will be “weak spots” that when a high current tries to push through, it causes a very local high temperature that can cause a “catastrophic” burn out of the entire filament.

If you’ve ever blown up and deflated a balloon repeatedly, you might know eventually the balloon will be weakened and pop before it gets fully inflated on the last attempt. Flipping the light switch on and off repeatedly is similar.

Because in incandescent Light bulbs, when you turn them on theres a sudden voltage spike that does more damage to the filament, the Part actually glowing, than continued Operation.