Everest College Commercial - Hood Variant
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haha....oh man....hahaha...NSFW due to language, but, man....hahahahhaahha
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Sep 3
Sep 3
Why do light bulbs burn out just as they’re turned on?
Why do light bulbs burn out just as they’re turned on?
Light bulbs are living on borrowed time, but why do their timers tend to expire just as you turn on a light, instead of flickering out randomly?
Everyone has had the experience of coming home from a long day, turning on the lights, and having the light bulb sputter at them as it flickers out. Fewer people have seem them randomly fizz out in the middle of the evening, after they've been on for a while.
Light bulbs give off light by pumping electric current through a thin tungsten filament. The filament heats and gives off light. Over time, the filament oxidizes and becomes more and more brittle, until it breaks apart and the bulb goes out. Since the oxidation occurs gradually and builds up, the light bulb should give out randomly, at any time. As anyone who lives in a house with electricity knows, this is not the case.
Tungsten gains resistance as it heats. Resistance is the amount of ‘push back' a material has against an electric current. The only thing that heats tungsten in a light bulb is electric current flowing through it. Imagine if a rubber hose gained strength only after water flowed through it. After some use, it would be able to handle a heavy stream of water. At first, though, it would bulge and strain like a water balloon before regaining its shape. Unless the rubber is in good condition, it will snap. In the same way, a tungsten filament is overloaded with current in the first few seconds after being turned on. The heat causes it to expand, and the filament experiences thermal stress, the strain of the material trying to expand due to sudden changes in temperature. Unless it is in good condition, it snaps.
What's more, over time, the filament becomes uneven. At certain points along the filament, the tungsten evaporates, thinning the filament more and more. At other points, the coils of the filament get pushed close together. When the high level of current surges through a stretch of wire even thinner than the rest of the filament, the heat builds up even faster than the rest of the filament. When it heats a section of coils pressed close together, the heat between them can't dissipate as quickly as it does in the rest of the bulb. The filament breaks or burns or simply melts.
It turns out that the average light bulb is not designed to be turned on. It's meant to already be on. The initial stress on the tungsten filament is far higher than the light bulb can handle. Those who wish to prolong the lives of their bulbs for ecological or sentimental reasons can pre-warm them before turning them on to a cozy 2,000 degrees before switching them on.
Top image by Andrew Price.
Your version of Internet Explorer is not supported. Please upgrade to the most recent version in order to view comments.I recall reading once very long ago that turning on and off the light switch takes about 4 minutes off the life of the bulb.
The thought was, if you were going to leave the room for less than 4 minutes, you should actually leave the lights on, because it would make your light bulbs last longer than if you shut them off and turn them on again. Replyomgwtflolbbqbye promoted this comment
I always feel weird when that happens, like I could have prolonged the life of the bulb if I'd flipped the switch more gently and added a kind word or something. Reply
"The light that burns twice as bright, burns half as long. And you have burned so very, very brightly, Roy" Reply
Once, when turning on a bathroom light, the bulb (seemingly) shot out of its fixture straight down into the bathroom sink where it proceeded to explode, mostly just in the sink, but bits and pieces (as it would later turn out) ended up in the bath mat. At the time, all I could do was laugh. Leaving it there and washing my hands to get back to what I was doing was a good idea at the time, but forgetting it was there a few hours later was not a whole lot of fun. Reply
There is a light in my apartment that I never turn off, ever, but I still occasionally have to change the bulb. So, EXPLAIN THAT DOCTOR SCIENCE!!!lol I kid, but seriously, I have to change it at least once every 6 months, which doesn't seem like any more time that a lightbulb I normally turn on and off. Reply
So its thermal stress.How about prolonging their by using dimmer switches at startup? gradully crank up the wattage going to the bulb? Reply
In the most typical cases. the tungsten is not oxidizing; the bulbs are not filled with air, but with argon and perhaps some nitrogen.Wikipedia goes into detail:
[en.wikipedia.org] Reply
Resistance is a physical property of matter to which degree it impedes the flow of electrons.At least that's what I told my students.
Also, the fact that there is oxygen in the bulb (it isn't a perfect vacuum) helps. Reply
I always wondered about that.
But can you answer me this:I live in an old building, and as far as I know, the electrical wiring hasn't been changed since the building was build, some 80 odd years ago. Does that have anything (and what, if it does) to do with the fact that light bulbs can't seem to last more than a month and a half at best? Reply
I'm surprised, usually these columns are right on the mark but this one couldn't be more wrong.It's actually because the lightbulbs hate me. Reply
How about explaining why those energy saving compact fluorescent bulbs, which costs much more and are suppose to last many years, burn out within a year? ReplyFrankN.Stein promoted this comment
There's a lightbulb that has been continuously lit since 1901.hdgotham (Hannah Wilson) promoted this comment
I say planned obsolescence by the money hungry light bulb association of lighting , designed specifically to have a short shelf life in order to keep you the consumer buying more!Case in point world's oldest light bulb is still burning...
If you build something that lasts for ever how can you continue to make a profit I ask you! And Profit is everything! Reply
Ah, my hypothesis is correct!
...Is it still a hypothesis if it's just something you always assumed? Reply
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Just happened to me...strange.
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Sep 2
Baby!! 8/21/10 Toronto - Justin Bieber - My World Tour 2010
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you might hate the guy, but he sure knows how to work a crowd.....
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Aug 27
Jersey Shore Meets Family Circus in Jersey Circus :: Blogs :: Awesome of the Day :: Paste
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Like Kanye West Tweets with New Yorker cartoons, Jersey Circus takes old Family Circus cartoons and adds quotes from Jersey Shore. You don’t have to be a fan of the show to appreciate the discordant humor (I’ve never seen an episode). But you’ll never look at little Joey the same way again. Some of our favorites so far but visit Jersey Circus to see them all.
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