Question for electrical wizards regarding light bulbs.

[Rolo Tomassi]

Why is it that light bulbs only burn out when they're turned on? Have you ever known a light bulb that's on and doing fine to suddenly burn out? I haven't.

[ISUFan98]

It's the power surge that causes the filament to break.

[funnelcake]

Seriously, you have never seen a light bulb burn out?

[Rolo Tomassi]

It's the power surge that causes the filament to break.

That's what I suspected. So what that means is that given a constant and endless supply of electricity, a light bulb will stay on forever.

[ISUFan98]

The world's oldest operating lightbulb.

At the Livermore, CA fire station.

109th year of operation.

http://www.centennialbulb.org/photos.htm

[ISUFan98]

It's the power surge that causes the filament to break.

That's what I suspected. So what that means is that given a constant and endless supply of electricity, a light bulb will stay on forever.

Not necessarily. Eventually most light bulbs will burn out.

[funnelcake]

It's the power surge that causes the filament to break.

That's what I suspected. So what that means is that given a constant and endless supply of electricity, a light bulb will stay on forever.

Not necessarily. Eventually most light bulbs will burn out.

Vibrations or weak spots in the tungsten filaments eventually get too hot and burn through.

[Rolo Tomassi]

The world's oldest operating lightbulb.

At the Livermore, CA fire station.

109th year of operation.

http://www.centennialbulb.org/photos.htm

Interesting excerpt:

"The Centennial Light," as it's now known, still hangs 15 feet above the fire trucks in Station #6 on East Avenue. It has outlasted three previous fire stations, even though its original task -- enabling the firefighters to see the equipment at night -- has long since been passed to younger, more robust bulbs. It gives a faint glow, equal to about three candles, and it has almost never been turned off. These are the keys to its longevity. Bright bulbs burn out faster, and they almost always blow when you flick on the switch. If you used only 4-watt bulbs to light your home, and you had a dedicated power supply (as does The Centennial Light), your lamps might last a hundred years, too.

As dim as it may sound, the best way to keep a light bulb burning is to never turn it off.

[TallGrass]

LED bulbs will pretty much last forever with regular on/off cycling.

[Tripper Harrison]

I'm exaggerating a little, but the Centennial Bulb also has a filament that is about as thick as a pencil.