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Long Life Lamp
Traditionally, lightbulbs were made to last 1000 hours. This was an industry standard and light bulbs were often guaranteed to last 1000 hours, which is reasonable. However, some people said it was an artificial life time, and that the light bulb companies were deliberately making lamps which had 1000 hours as the failure time of the bulb so they would stay in business! This was a popular folklore belief, and sometimes the story extended to the idea that lightbulb companies would buy up any invention of everlasting lightbulbs which threatened the fragile market of artificially short life bulbs.
It's a bit unfair in a way, as a basic lightbulb costs about the same as a newspaper, and that only lasts one day. In contrast, a 1000 hour lightbulb is rated to last 40 days and 40 nights continuous use, as that's how long 1000 hours is.
In my experience, some of the cheap bulbs don't last 1000 hours and fail much earlier. Admittedly they are guaranteed to last 1000 hours, but in practice, who's going to measure it?! Not many people will, and those that ask for their money back are in a small minority in comparison to the average customers who the supermarkets rely on to buy and forget!
One of the conspiracy theory notions of deliberately fallible lightbulbs involved the idea that the lamp-making companies deliberately allowed a small amount of gas or air in the bulb so it would fail. I've checked this, and although small amounts of gas exist in lightbulbs that does not mean it's doing any harm! It might be a small amount of harmless gas of a relatively inert nature, such as Argon. A while ago there were light bulbs which were stated to be "gasfilled", ie they were made with some harmless gas inside which had a beneficial effect.
Filament lamps, from what I have seen, fail because the filament becomes frail and at some point it breaks. It's made of very thin tungsten wire wrapped round in a coil, and then the coil is wrapped round in a coil. The whole thing is vibrating around in the earth's magnetic field and heated up to a couple of thousand degrees and eventually it snaps.
If a lightbulb has a filament, its life can be extended by a few techniques. One such method involves running it off DC. The difference between AC and DC can make a difference. If you put a magnet near a lightbulb running off AC, you'll see the filament vibrates quite a lot because the alternating current through the coil has a magnetic effect which interacts with the magnetic field from the magnet. Even with no artificial magnet, the earth's magnetic field makes lightbulb filaments vibrate just a little bit, whereas if you run them off DC, this doesn't happen. The filament will still break at some time, but it will last longer than on AC. Perhaps someone would like to perform a proper scientific experiment with a statistically significant sample size! It needs to be proper smoothed DC; it's no good just full-wave rectifying it!
Another technique for increasing the lifetime of a lightbulb is to under-run it. This works surprisingly well at prolonging the life span of a light bulb, but it tends to reduce its efficiency. That's because the filament is not quite so hot and produces a lower "colour temperature" and generally produces emissions more towards the heat end of the spectrum. This is good for museum lighting, but not a major advantage for domestic use. The problem with this is that it's more important to save expensive electricity than it is to make a cheap lightbulb last longer! This is explained further on the review of economy lightbulbs
On the theme of under-running lightbulbs, there was a time when a company produced a bulb which was rated at 2000 hours, and this was done by over-engineering the filament so in effect it was under-run. It worked, lasted at least 2000 hours, but was slightly less bright. Unfortunately the lower brightness was not made by using less electricity, but by running the filament at a lower temperature. It still gave off the energy as heat.
Long life lightbulbs became more common with the invention of the fluorescent tube. This lasts much longer than a filament bulb, and is more efficient, although it requires more electronics in the fitting. The idea was further extended when energy efficient lightbulbs were created. These are about the size of a lightbulb but are electrically more like a fluorescent lamp. The tube has been made smaller and turned around in loops or a coil, and the electronics is miniaturised and fits in the base. As it's classed as "a lightbulb" rather than "a fluorescent tube" the rated hours are boasted on the box, and figures of 6000 hours or 8000 hours are typically mentioned. So, lasts much longer than a traditional filament lamp, but more importantly uses less electricity. As with life itself, it is the quality, not simply the length, that matters!
I've always liked the idea of having NEON LIGHTS. These look great in a house and are a good talking point! They are reasonably efficient, and have no filament to burn out as the light is produced by electrical excitation of exotic gases. (Although they are termed "neon lights", it's a generic term, and the bulbs can contain other gases, often in combination, to get the different colours). Although this looks great, and it's efficient, it wouldn't do for most people because of the bright colours. Most people prefer their lighting to be nearer to white light, and they even grumble sometimes if the roads are lit by bright orange lights!
In terms of lifetime, neons last very well. A neon I put up thirty years ago is still lit, and it's been powered up continuously since then. That's hundreds of thousands of hours.
LEDs are a more recent development, and although they've been more associated with indicator lamps, the technology has improved and it's now possible to get very bright LEDs, available in white, set up as a lightbulb. LEDs are Light Emitting Diodes, a species of semiconductor device which has transistor-like characteristics but also gives off light.
The LED is more efficient than a filament bulb, and I've not yet seen one that's died of old age.
As with the neon, the LED requires a ballast, which is just an extra component which is like the electrical equivalent of packing or a shock absorber. It usually comes as part of the device, already fitted.
You can get 100 watt LED units, although they are considerably more expensive than a basic lightbulb or even an energy efficient lightbulb. I'm hoping some high-power LED lamps are going to be available at the page of Lighting
There is a protest against the 100 watt lightbulb ban going on!