How does a fluorescent bulb burn out?


Old 03-17-07, 03:23 PM
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Location: CT
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How does a fluorescent bulb burn out?

I was curious on how a fluorescent bulb burn out.
Something you probably would never think of.

..Does the filament(s) just burst or burn and
that's what makes the tubes' end(s) black?

..I also wanted to know what makes the swirling
of brighter light at the end of the tube mean??
(I've noticed sometimes that it is when the bulb
comes to the end of its life and it hasn't gone out yet)
((What is swirling inside it? Sometimes it's made up of
motion only on one side and sometimes it's most of the tube)

..Why does a whole fixture, even w/ 2 or more bulbs, cycle on and off
periodically, and then it could go for months working fine and then it does the same faults again. it the ballast going out very slowly and it is an indication of the ballast
failing and a safety setting shuts the fixture off so it does not overlamp?

just curiousity..thanks..
Old 03-17-07, 05:00 PM
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Wikipedia explains the four most common methods by which the bulb eventually fails: (1) emissions mix runs out, (2) failure of the integral ballast electronics, (3) failure of the phosphor, and (4) tube runs out of mercury. The dark ends of the tube are caused by the first of these types of failures, probably the most common failure mode.

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