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Re: [Amps] filament instant heating query

To: Charles Harpole <k4vud@hotmail.com>, <amps@contesting.com>, David Springer <dspringer@cfl.rr.com>
Subject: Re: [Amps] filament instant heating query
From: Bill Fuqua <wlfuqu00@uky.edu>
Date: Fri, 15 Jun 2012 00:49:07 -0400
List-post: <amps@contesting.com">mailto:amps@contesting.com>
Myth Busters did an experiment with light bulbs to see how they were 
affected by switching some on and off and others left on.
Practically no difference.
   I believe this mostly started with light bulbs because when once the 
filament gets so thin at some point due to the evaporation of the
tungsten the next time you turn it on and you have a surge of current in 
the lamp it burns into. This thin area has a higher resistance
than the rest of the filament and gets hotter.
   I don' think there is any real rocket science, molecular physics or 
quantum mechanics to it.
73
Bill wa4lav


At 03:59 AM 6/15/2012 +0000, Charles Harpole wrote:

>to check on a supposition............
>
>
>
>It appears possible that the sudden application of voltage to a tube 
>filament causes degradation of the filament.
>
>
>
>What seems to happen?  Is it possible that the very rapid heating of a 
>filament could cause so much quick molecular action (rapid increased 
>bouncing around of the molecules) that the shape of the filament could be 
>changed?  A deformed filament could then be too close to other components 
>to cause an arc, perhaps?
>
>
>
>Or is the action on the atomic level...i.e., does heat change the actions 
>of electrons in an atom?
>
>
>
>But, maybe the filament rapid heating works just fine, and all of the 
>"slow start" "inrush protection" circuits are a waste?
>
>
>
>Another inquiring mind wants to know.
>
>73,
>
>Charles Harpole
>k4vud@hotmail.com
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