Jim Yanik wrote:

snipped


Ordinary incandescent bulb filaments gradually erode and become thinner,and
finally,the turn out surge is what kills them.


Yeah, and sometimes when they burn out you'll get a "tungsten arc"
effect where an arc starts burning between the broken filament ends and
keeps melting back along the two filament pieces until it is arcing
directly between the filament connecting leads. That arc can be a low
enough resistance to cause a fuse to pop or a breaker to snap.

When you get a "tungsten arc" it usually occurs just as you switch on
the bulb and you may notice a brief brighter than normal flash of light,
it's all over in a moment.

Some light bulbs are/were made with a "fuse link" built into one of the
leads intended to blow under those arcing conditions to avoid your
having to reset a breaker or replace a fuse.

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"As long as there are final exams, there will be prayer in public
schools"