My father and I have been having a little argument, and while this is certainly not the cutting edge scientific stuff frequently discussed on here I'd like the opinion of someone perhaps better informed than myself. We just bought a new light fixture for the kitchen, it can hold 5 bulbs. If we put in 5 25 watt bulbs will this yield more, less, or the same amount of light as a 125 watt bulb?
geni
Anti-homeopathy illuminati member
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I suspect that the biggest factor in determing the difference is the light to heat ratio. I suspect that a 125 watt bulb will be hotter but the 25 watt bulbs will have a greater surface area which should increase the amount of heat radated. I suspect that this will make the 25 watt bulbs less effecient so the 125 watt bulb will be brighter.
Sits back and waites to be wacked by someone who athcerly knows something about physics.
Sits back and waites to be wacked by someone who athcerly knows something about physics.
I found a web page that seems to say high wattage incandescent bulbs are more efficient than low wattage ones. I'm having trouble posting the URL here; the URL contains a character sequence that shows up as a smilie. Use Google to search for "Bulletin TP-110R1". Only one result is returned. Click on "View as HTML". Look at the first two columns of the table at the top of page 2.
Well, the higher powered the lamp (with a fixed input voltage) the thicker the fillament, and the higher temperature it can run at, so if we're talking all incandescent here, the higher power lamp that runs at the same voltage will be somewhat more efficient, simply because it runs at a slightly higher temperature, and as such will be more efficient.
Skeptoid said:
Another point that must be made is that "long-life" incandescents get their life by cooling down the filament a bit. Since the curve of radiation vs. temperature is pretty steep, that tends to reduce their output by quite a bit.
Somewhere in my old AT&T accounts, long ago, I had all of the temperature, voltage, etc sensitivities stored away. I've no idea where that might be nowadays.
On a less technical level- 5 25 watt bulbs mounted in a cluster will occult one another from certain angles. The light will be uneven.
One 125w bulb should give a more even distribution.
There is a huge subjective element to how acceptable illumination is. Some spots, for instance, actually make a room feel darker, because they cast shadows as you move around.
One 125w bulb should give a more even distribution.
There is a huge subjective element to how acceptable illumination is. Some spots, for instance, actually make a room feel darker, because they cast shadows as you move around.
ktesibios
Worthless Aging Hippie
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jj said:
Another point that must be made is that "long-life" incandescents get their life by cooling down the filament a bit. Since the curve of radiation vs. temperature is pretty steep, that tends to reduce their output by quite a bit.
Somewhere in my old AT&T accounts, long ago, I had all of the temperature, voltage, etc sensitivities stored away. I've no idea where that might be nowadays.
Duuno about the temperature sensitivities, but a few rule-of-thumb relationships about the effects of applied voltage for small hard-vacuum bulbs:
power input varies approximately as V^1.6 (this is because filament resistance increases as filament temperature goes up; if the filament resistance were constant the power would be proportional to V^2)
visible light output varies approximately as V^3.4
life varies approximately as 1/(V^13).
Most of the long-life bulbs I've seen are designed to draw their rated power at 130V. Run them on a typical 120V source and they last a lot longer that they would at their design voltage.
The Central Scrutinizer
Penultimate Amazing
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How many Skeptics does it take to screw in five 25 watt light bulbs?
