Why do light blubs only burn out when you turn on a light?
- Thread starter AccruedExpenditure
- Start date
Because that is when the power surges and breaks the coil
Also, interesting knowledge I found:
"Most lights flicker all the time but you don't realize it because of a psychological phenomenon called 'flicker fusion frequency.' The flicker fusion frequency is usually about 25 hertz (cycles-per-second). A light that turns on-and-off (flickers) faster than 25 times per second will appear to be on, steady. Your home's 60 cycle AC turns on and off 120 times a second, though it is only off momentarily, it's increasing or decreasing the rest of the time. If you use a dimmer switch it turns the power to the light completely off for a while 120 times a second. Of course, incandescent lights don't have time to cool down to dark during these brief off times but, they dim and brighten. Early movies used too few frames per second, that's why they flicker. Whereas, later movies are frequent enough; so, though there are totally black moments between each frame, you don't see any flicker.
Note: The 25Hz is an ordinary/average value. It varies based on the brightness/intensity of the source and can go as high as 50-60Hz for very bright sources. "
Also, interesting knowledge I found:
"Most lights flicker all the time but you don't realize it because of a psychological phenomenon called 'flicker fusion frequency.' The flicker fusion frequency is usually about 25 hertz (cycles-per-second). A light that turns on-and-off (flickers) faster than 25 times per second will appear to be on, steady. Your home's 60 cycle AC turns on and off 120 times a second, though it is only off momentarily, it's increasing or decreasing the rest of the time. If you use a dimmer switch it turns the power to the light completely off for a while 120 times a second. Of course, incandescent lights don't have time to cool down to dark during these brief off times but, they dim and brighten. Early movies used too few frames per second, that's why they flicker. Whereas, later movies are frequent enough; so, though there are totally black moments between each frame, you don't see any flicker.
Note: The 25Hz is an ordinary/average value. It varies based on the brightness/intensity of the source and can go as high as 50-60Hz for very bright sources. "
Yes, they will. The coil will still burn/break eventually. Go grab a light bulb and look inside to see two sides connected via a wire. When that coil/wire breaks/burns/gets overused - it pops off a side and the connection is no longer there to generate the light.
dullard
Elite Member
- May 21, 2001
- 26,192
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It isn't just the power surge.
That is when the cold metal suddenly heats and expands. Repeated sudden expansion/contraction of metal leads to small fractures. Once when you turn it on, the fractures are sufficient that the expansion pulls it beyond its weakened limits.
Small fractures rarely break when you stop pulling on them (light turning off).
Over time, heat will also weaken the metal. But this is a long slow process. A lightbulb will generally fail (in normal usage) from the expansion/contraction before it fails due to long exposure to heat.
That is when the cold metal suddenly heats and expands. Repeated sudden expansion/contraction of metal leads to small fractures. Once when you turn it on, the fractures are sufficient that the expansion pulls it beyond its weakened limits.
Small fractures rarely break when you stop pulling on them (light turning off).
Over time, heat will also weaken the metal. But this is a long slow process. A lightbulb will generally fail (in normal usage) from the expansion/contraction before it fails due to long exposure to heat.
they'll probably last really long if you kept them on forever.. isn't the first light bulb ever still burning at the smithsonian or something?
i thought it had to do with the filament evaporating at an uneven rate, which makes parts thinner than others
hot filaments have more resistance than cold, the thin part heats up faster while the thick part is still cool
thin part = weak and high resistance when bulb is first turned on
thicker part = stronger and less resistance when bulb is first turned on
hot filaments have more resistance than cold, the thin part heats up faster while the thick part is still cool
thin part = weak and high resistance when bulb is first turned on
thicker part = stronger and less resistance when bulb is first turned on
They will last a very, very long time.
http://www.centennialbulb.org/
This is an extremely low wattage bulb. I think the backlight on my cell phone puts out more light, but 100 years...
Viper GTS
gsellis
Diamond Member
- Dec 4, 2003
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Hmmm.... I have heard it explained a little differently. The wire does weaken and fracture as it spits off tungsten. The dark stain and spots in the bulb are part of the wire. When you turn it on, the extreme temp change and current cause the wire to vibrate wildly. That is the weakest time, with the most violent point, on a wire that has been shedding parts of itself off. The arc happens as it seperates for the big flash. Fortunately, no Earth shattering kaboom.
- Oct 30, 2000
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Rubycon
Madame President
- Aug 10, 2005
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This just in from the Weather Control Agency:
For years the electrical utility companies have led the public to believe they were in business to supply electricity to the consumer, a service for which they charge a substantial rate. The recent accidental acquisition of secret records from a well known power company has led to a massive research campaign which positively explodes several myths and exposes the massive hoax which has been perpetrated upon the public by the power companies.
The most common hoax promoted the false concept that light bulbs emitted light; in actuality, these 'light' bulbs actually absorb DARK which is then transported back to the power generation stations via wire networks. A more descriptive name has now been coined; the new scientific name for the device is DARKSUCKER.
This newsletter introduces a brief synopsis of the darksucker theory, which proves the existence of dark and establishes the fact that dark has great mass, and further, that dark particle (the anti-photon) is the fastest known particle in the universe. Apparently, even the celebrated Dr. Albert Einstein did not suspect the truth.. that just as COLD is the absence of HEAT, LIGHT is actually the ABSENCE of DARK... scientists have now proven that light does not really exist!
The basis of the darksucker theory is that electric light bulbs suck dark. Take for example, the darksuckers in the room where you are right now. There is much less dark right next to the darksuckers than there is elsewhere, demonstrating their limited range. The larger the darksucker, the greater its capacity to suck dark. Darksuckers in a parking lot or on a football field have a much greater capacity than the ones in used in the home, for example.
It may come as a surprise to learn that darksuckers also operate on a celestial scale; witness the Sun. Our Sun makes use of dense dark, sucking it in from all the planets and intervening dark space. Naturally, the Sun is better able to suck dark from the planets which are situated closer to it, thus explaining why those planets appear brighter than do those which are far distant from the Sun.
Occassionally, the Sun actually oversucks; under those conditions, dark spots appear on the surface of the Sun. Scientists have long studied these 'sunspots' and are only recently beginning to realize that the dark spots represent leaks of high pressure dark because the Sun has oversucked dark to such an extent that some dark actually leaks back into space. This leakage of high pressure dark frequently causes problems with radio communications here on Earth due to collisions between the dark particles as they stream out into space at high velocity via the black 'holes' in the surface of the Sun.
As with all manmade devices, darksuckers have a finite lifetime caused by the fact that they are not 100% efficient at transmitting collected dark back to the power company via the wires from your home, causing dark to build up slowly within the device. Once they are full of accumulated dark, they can no longer suck. This condition can be observed by looking for the black spot on a full darksucker when it has reached maximum capacity of untransmitted dark... you have surely noticed that dark completely surrounds a full darksucker because it no longer has the capacity to suck any dark at all.
A candle is a primitive darksucker. A new candle has a white wick. You will notice that after the first use the wick turns black, representing all the dark which has been sucked into it. If you hold a pencil next to the wick of an operating candle, the tip will turn black because it got in the way of the dark flowing into the candle. It is of no use to plug a candle into an electrical outlet; it can only collect dark.. it has no transmission capabilities. Unfortunately, these primitive darksuckers have a very limited range and are hazardous to operate because of the intense heat produced.
There are also portable darksuckers called flashlights. The bulbs in these devices collect dark which is passed to a dark storage unit called a battery. When the dark storage unit is full, it must be either emptied (a process called 'recharging') or replaced before the portable darksucker can continue to operate. If you break open a battery, you will find dense black dark inside, evidence that it is actually a compact dark storage unit.
For years the electrical utility companies have led the public to believe they were in business to supply electricity to the consumer, a service for which they charge a substantial rate. The recent accidental acquisition of secret records from a well known power company has led to a massive research campaign which positively explodes several myths and exposes the massive hoax which has been perpetrated upon the public by the power companies.
The most common hoax promoted the false concept that light bulbs emitted light; in actuality, these 'light' bulbs actually absorb DARK which is then transported back to the power generation stations via wire networks. A more descriptive name has now been coined; the new scientific name for the device is DARKSUCKER.
This newsletter introduces a brief synopsis of the darksucker theory, which proves the existence of dark and establishes the fact that dark has great mass, and further, that dark particle (the anti-photon) is the fastest known particle in the universe. Apparently, even the celebrated Dr. Albert Einstein did not suspect the truth.. that just as COLD is the absence of HEAT, LIGHT is actually the ABSENCE of DARK... scientists have now proven that light does not really exist!
The basis of the darksucker theory is that electric light bulbs suck dark. Take for example, the darksuckers in the room where you are right now. There is much less dark right next to the darksuckers than there is elsewhere, demonstrating their limited range. The larger the darksucker, the greater its capacity to suck dark. Darksuckers in a parking lot or on a football field have a much greater capacity than the ones in used in the home, for example.
It may come as a surprise to learn that darksuckers also operate on a celestial scale; witness the Sun. Our Sun makes use of dense dark, sucking it in from all the planets and intervening dark space. Naturally, the Sun is better able to suck dark from the planets which are situated closer to it, thus explaining why those planets appear brighter than do those which are far distant from the Sun.
Occassionally, the Sun actually oversucks; under those conditions, dark spots appear on the surface of the Sun. Scientists have long studied these 'sunspots' and are only recently beginning to realize that the dark spots represent leaks of high pressure dark because the Sun has oversucked dark to such an extent that some dark actually leaks back into space. This leakage of high pressure dark frequently causes problems with radio communications here on Earth due to collisions between the dark particles as they stream out into space at high velocity via the black 'holes' in the surface of the Sun.
As with all manmade devices, darksuckers have a finite lifetime caused by the fact that they are not 100% efficient at transmitting collected dark back to the power company via the wires from your home, causing dark to build up slowly within the device. Once they are full of accumulated dark, they can no longer suck. This condition can be observed by looking for the black spot on a full darksucker when it has reached maximum capacity of untransmitted dark... you have surely noticed that dark completely surrounds a full darksucker because it no longer has the capacity to suck any dark at all.
A candle is a primitive darksucker. A new candle has a white wick. You will notice that after the first use the wick turns black, representing all the dark which has been sucked into it. If you hold a pencil next to the wick of an operating candle, the tip will turn black because it got in the way of the dark flowing into the candle. It is of no use to plug a candle into an electrical outlet; it can only collect dark.. it has no transmission capabilities. Unfortunately, these primitive darksuckers have a very limited range and are hazardous to operate because of the intense heat produced.
There are also portable darksuckers called flashlights. The bulbs in these devices collect dark which is passed to a dark storage unit called a battery. When the dark storage unit is full, it must be either emptied (a process called 'recharging') or replaced before the portable darksucker can continue to operate. If you break open a battery, you will find dense black dark inside, evidence that it is actually a compact dark storage unit.
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