Breaking the myth: Incandescent bulbs don't last

[Joods]

We do not use incandescent bulbs in our home. We use those spiraly ones. But those fuckers break too.

[Losty]

I don't like the spirally ones. They never seem bright enough.

[Joods]

They eventually get bright enough. I think they are designed to gradually brighten after they are turned on.

Damn. That sounded dirty. LOL

[Losty]

I am designed to gradually brighten once I am turned on.


On a serious note, I don't know why. I try not to leave lights on. I can't see myself waiting around for one to get bright enough. Sound like a pain.

[Aractus]

Just some things that come to mind concerning your calculation -
It is conceivable that the 200W bulb will draw a bit more than 60W (i.e.  (120/220)^2 times the power) at reduced voltage because the resistance will be noticeably lower at the new operating point as compared to 200W. Also, it is possible that the 200W bulb running with 60W will have lower filament temperature than a regular 60W bulb, thus reducing the efficiency in visible light, so there might be a trade off between longevity and efficiency. Those are just ideas, I don't know how big these effects are.

p.s. standard voltage has been 230V for some time now, at least in Germany

Yeah you're right about that - the filament resistance is variable to heat, therefore instead of 59.5W it could draw say 62W or something like, it's difficult to know exactly without running a measured test. What it won't be, however, is any less than 59.5W since heat increase the resistance in the filament.

[pocaracas]

Heat increases the resistance of the filament?
Are you sure? That sounds a bit counter-intuitive, to me... heat should promote electron mobility, thus leading to less resistivity....

[AFTT47]

Some materials increase with resistance with heat while others decrease.

A cold filament has only about 1/8 the resistance of a hot one or even less, depending on the specific filament. When an incandescent lamp is first turned on, there is a huge current surge which lasts a fraction of a second until the temperature spikes up.

[Aractus]

What doesn't change, however, is the efficiency. It still produces the same amount of heat and light per Watt consumed.

[Anomalocaris]

Yes, but reducing the voltage reduces the watts consumed, which reduces the temperature of the same filament radiating surface, which shifts the emission further to the infrared, which means it puts out even lower light to heat ratio.

Incidentally, there is a recent report of the successful proving of concept of a super incandescent bulb which promise to put out 40% of its total power draw in visible light. Such a bulb would be much more efficient than even LEDs.

The basic idea is this bulb wraps the filament in a nanotech manufactured shell that reflects IR but is transparent to visible light. Only visible light gets through the shell. Most IR is reflected back to the filament, where it is re-absorbed and the re-radiated at a slightly higher average frequency, thus extracting a few visible light photons from pure IR photons. The shell itself is much larger than the filament, remains cool, and radiates comparatively little IR to the outside.

[brewer]

I just got this thing floating above my head that constantly glows.