Re: Defective Bulb Tripping Ckt Breaker: How Possible ?
- From: Sam Goldwasser <sam@xxxxxxxxxxxxxxxxxxx>
- Date: 31 Oct 2006 19:47:11 -0500
Yukio YANO <yano@xxxxxxx> writes:
N Cook wrote:
Robert11 <rgsros@xxxxxxxxx> wrote in message
news:AaadnUKll9619trYnZ2dnUVZ_sednZ2d@xxxxxxxxxxxxxx
Hi,hall
Boy, this is a funny one.
Wife turned on a hall light switch last night, big flash by one of the
lights, and the ckt breaker tripped.
Was about 2 days since putting in a new bulb there.
Was the el-cheapo brand picked up at CVS, and made in China.
Replaced the bulb with a GE one, and so far everything seems O.K.
Question: I can't imagine how anything, like e.g., a broken filament
perhaps, can short out the circuit.
But, perhaps ?
Can anyone think of a bulb failure mechanism that might trip the breaker ?
Or, might this be just a coincidence ?
Thanks,
I'm only going by memory and may have it a bit wrong.
A tiny part of the filament wears to the point it creates a hot-spot which
rapidly gets worse causing the first part of the intense flare. In that
super-heated process a plasma state is formed within the bulb. In a plasma
state the effective conductivity across the 2 filament suspension end points
becomes orders of magnitude less than the original filament resistance so
for very short duration , can pass tens or hundreds of amps.
It is the same mechanism whereby a lightning discharge through air can pass
millions of amps through a channel that is only about 1/2 inch in diameter
which no metal could pass. The same discharge passing into the right soil/
conditions leaves a yards long but same 1/2 inch wide hollow tube punched
through the ground, see keyword fulgurite.
Nope, he's got it right. Once the arc forms, it may not stay between
the broken ends. Because the arc is a negative resistance, increasing
the current lowers its resistance. So, it can grow towards the ends of
the filament in an instant and then it's nearly a short circuit.
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- Defective Bulb Tripping Ckt Breaker: How Possible ?
- From: Robert11
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- From: N Cook
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- From: Yukio YANO
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