Why is it lightbulbs have to be replaced every so often but seemingly small lights (like those that indicate a TV is off/on) can last for 10 years or more?


Why is it lightbulbs have to be replaced every so often but seemingly small lights (like those that indicate a TV is off/on) can last for 10 years or more?

In: Technology

Older light bulbs are incandescent lights. They make light by heating a small metal filament with electricity. Over time that filament wears out and eventually breaks.

Small lights like the power light on an appliance have been mostly LEDs for probably 30 years now. LEDs have a *much* longer lifespan, but until the last few years were pretty expensive to use in applications where you needed an actual bright light source.

Now LED light bulbs are getting pretty cheap, and those will go years and years without needing replacement.

Some small lights are actually LEDs, these don’t operate on the same principal as lights.

Light bulbs, traditionally anyway, use a filament to create light. Electricity is passed through the filament which then lights up because of heat. Over time the filament oxidizes, which makes it brittle, and eventually it can’t handle the flow of electricity and it breaks; it burn out.

LEDs operate differently. They don’t have a filament, but instead use semiconductors to pass electricity over. The semiconductor doesn’t get hot, or oxidize, and only produce light because of the electrons passing over the material. A component can fail, causing the LED to fail, but it won’t “burn out”. They can degrade over time with use however, but it takes much longer. Some LEDs can last decades depending on how frequently they’re used or how bright they need to be.

It’s sort of like using a rope to tie something up versus using a metal lock. A rope wears down every time you use it, and it weathers just by being used. Eventually it’ll fray and break. A metal lock in the other hand will last much longer because it has fewer parts to wear down. They’ll both break, but the rope takes longer because it suffers more wear and tear in its use than metal locks do.

With a set amount of voltage in a home (say, 120volts), a 60w incadescent bulb will draw 0.5 amps of current. A similar output led is only, say, 6 watts. On a 120v circuit it will draw 0.05 amps, one tenth. Amperage produces heat which is an enemy of electrical components. Your indicating lights on electronics have their ratings way lower than is needed for a bulb that goes into a lamp as well.

Im sure there is more complex explanation since i am a novice, but going off theory alone, that could explain it.

Lightbulbs convert electricity to light, or in more sciencey speak: they generate photons from electrons.

The lightbulbs you’re constantly replacing are incandescents and they’re woefully inefficient at generating photons with electrons, only about 10% actually goes to creating light. The other 90% of the electrons are used to keep a thin wire called the filament at a constantly high “light-emitting” temperature. The little electrons speed through the filament smashing into its molecules causing them to vibrate. Once they’re vibrating enough those molecules emit photons which we see as light. The filament is incredibly thin to funnel more electrons into it so fewer electrons are needed to reach the light-emitting temperature. This makes it more efficient, but it also very delicate and the vibrating molecules eventually break it.

The small lights on your TV are called LEDs. They generate photons from electrons with an entirely different mechanism called Electroluminescence. This method is far more efficient and does not generate heat so there’s no sudden failure.

Because they are built for the filament to break to keep the demand for bulbs, theres a bulb in California emoting light since 1901 and it never shuts off.