Q about light bulb shorting out.


I bought a replacement bulb for the front porch light, and when I turned it on, there was a loud POP and the house blacked out. There was some smoke and sparks as well...(from the light fixture). The circuit breaker got the lights back on...Did the new bulb somehow do this? I haven't tried another yet.....or is there a problem in the light fixture? (the light was working last night...the bulb blew out tonight)
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Bad socket, wires, connections, whatever. The socket is probably loose. Replace it, $5.00 and an hour of your time.
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Father Haskell wrote:

I'll second that.
The bulb may have suffered what's known as a "tungsten arc" failure. That's when the filament breaks and an arc starts between the broken ends which vaporizes the tungsten filament material into a conductive plasma. The arc continues melting back the ends of the filaments, with the current draw increasing as the filament ends get shorter and the plasma more concentrated until it's occuring between the filament support wires at which point the current is pretty damn high. It all takes place in a fraction of a second and it's not unusual for it to cause a breaker to open or a fuse (in old houses) to blow.
If you've ever switched on a light and had it fail immediately with a blinding white flash, you've witnessed a tungsten arc.
Years ago quality light bulbs were made with a necked down section in one of the base lead wires to serve as a fuse which would blow if a tungsten arc caused excessive current flow. I doubt if any of the junky bulbs they're selling now have that feature.
If you examine the socket and it's connections and they seem ok, just try another bulb.
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat \'57 EE)
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If it's a utility light, like a front porch fixture, replace it with a CFL.
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The bulb COULD have lost its seal, became open to air, the tungsten filament vaporizes at a point and disconnects, falls down and presents a very low resistance across the interior wires in the bulb base, makes a flash at the same time it's tripping the breaker.
Replace the bulb first, try again.

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