Re: Using mobile phone as an internet radio

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#39

From: Phil Hobbs
Date: Fri, 05 Oct 2012 22:36

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Jeff Liebermann wrote:
> 
> On Thu, 04 Oct 2012 10:03:21 -0400, Phil Hobbs
> <pcdhSpamMeSenseless@electrooptical.net> wrote:
> 
> >> Yep.  As I understand it (possible wrong), AC filaments break in the
> >> middle, mostly from vibration flexing.
> >
> >I don't think so, because there's no mechanism for that, as I said.  The
> >wire is fully annealed at all times, so there's no possibility of
> >progressive fatigue failure.
> 
> Oscillating filament light bulb:
> <http://www.youtube.com/watch?v=t_DwwNVA-7Q>
> Whether the earths magnetic field is strong enough to induce such
> oscillations is questionable.
> 
> While digging for the apparently mythical lifetime test data on
> incandescent light bulbs, I've found numerous theories on why
> filaments fail.  Tungsten evaporation, causing hot spots, is the most
> common.  One suggested that thermal cycling hardens the tungsten and
> makes it brittle.  Another suggested that the inrush current causes a
> mechanical shock if it hits at the 60Hz peak, instead of at the zero
> crossing.  Yet another speculates that the temperature differential
> between the hot filament, and the relatively cold mounting structure
> may cause cracking.
> 
> --

All of those except the hot spot mechanism assume that the tungsten
work-hardens in the bulb and then fails from fatigue.  However, that
isn't the case, because the annealing temperature of tungsten is about
1300 C, so the tungsten in a light bulb filament is always fully
annealed.

Cheers

Phil Hobbs


-- 
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net

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Date: Fri, 05 Oct 2012 18:36:08 -0400
From: Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>
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Subject: Re: Using mobile phone as an internet radio
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