Was Edisons original light bulb really designed to never run out?
This sounds like you’ve heard one of those “some guy invented a car that runs on water (but the auto industry had him rubbed out)” urban legends — i.e. that Edison invented a bulb with very long life, but the manufacturers prefer to produce bulbs that need replacement. There’s a grain of truth here, and that is — well, a bit from Wikipedia: Incandescent lamps are very sensitive to changes in the supply voltage. These characteristics are of great practical and economic importance…. 5% reduction in operating voltage will double the life of the bulb, at the expense of reducing its light output by 20%. This may be a very acceptable tradeoff for a light bulb that is a difficult-to-access location (for example, traffic lights or fixtures hung from high ceilings). So-called “long-life” bulbs are simply bulbs in which this tradeoff is designed in…. Operating a 100 watt, 1000 hour, 1700 lumen bulb at half voltage would ext
