TE> I don't know about cost, but for incandescents, the bulb will last much
TE> longer if left on, as opposed to constantly turning it on and off.  This
TE> is caused by the temperature change expanding and contracting the 
filament,
TE> making it brittle and shortening it's life.  Of course, the cost is very
I always though the main reason incadencense burned out was because when you 
turn any power swicth on, their is a slight surge in voltage, and I always 
firgured that extra bit of power was enough to burn the filament out, but I 
guess that the answer is that it is a combination of the 2 reasons.
--- GEcho 1.00
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** A related thread FOLLOWS this message.

FIDO MESSAGE AREA==> TOPIC: 274 PYROTECHNICS  Ref: D53S1580 Date: 05/03/96
From: JAN HICKEY                                            Time: 11:26pm
\/To: SCOTT HOFFMAN                                       (Read 6 times)
Subj: R: Re: How many light bulbs...

SH>I always though the main reason incadencense burned out was because when
SH>turn any power swicth on, their is a slight surge in voltage, and I alwa
SH>firgured that extra bit of power was enough to burn the filament out, bu
SH>guess that the answer is that it is a combination of the 2 reasons.
 
     Incandescent bulbs burn out at startup from a combination of two
factors.
          1.) Thermal shock. Sudden heating causes expansion, cooling the
               converse. The filament breaks either on expansion or
               contraction and fails catastrophically when power arcs
               across the gap.
 
          2.) Filaments have less resistance when cold than when hot.
               This acts to limit running current but starts the lamp
               quickly because there is a CURRENT surge at startup
               (accompanied by a voltage DROP BTW) which rapidly heats
               the filimant to its operating temp. Fatigue from the
               expansion and contraction of many heat cycles (see #1)
               eventually causes a thin section which heats before the
               rest of the filament and melts, resulting in an arc and
               catastrophic failure. The thin section heats first because
               it acts as an area of higher resistance like the thin part
               in the middle of a fuse.
 
     More than you probably wanted to know but I couldn't help flaunting
my good 7th grade science class education (1960-61).
 
                                        Dave Hickey
 
PS - I only wish my english/spelling instructor had done as good a job, of
course the science teacher had it easy, I was interested. D.H.
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FIDO MESSAGE AREA==> TOPIC: 274 PYROTECHNICS  Ref: D4U00001 Date: 04/23/96
From: TERRY S                                               Time: 05:26am
\/To: TOM EMBT                                            (Read 8 times)
Subj: How many light bulbs...

In case you're not connected to Fido references, the flame you got from an 
alias of Turiyan Gold, possibly Aubrey Presha or some user at 1:3603/361 
pretending to be the moderator here, is a fraudulent spam.  
The light thread may well be better suited for ELECTRONICS (though some 
theatrical related issues may be relevant here).  
The real moderator is Mark Buda (NOT Dan Buda) of 1:132/777.  
Terry
--- Maximus 2.01wb
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