[Phys-L] Re: light bulb transient

[John Clement <clement@HAL-PC.ORG>]

This still does not resolve the possibility that there is a flash when a
bulb burns out.  It is quite possible that there is local reduction in
resistance at the time the bulb is ready to burn out, and an increase in
temperature.  One can simulate this effect by carefully tapping a bulb to
short out some of the coils.  It will burn very brightly for a limited
period of time.  Guys used to do this with hall lights in the dorms.  Also
there is seems to be a definite tendency for bulbs to burn out when first
turned on, so there is likely some transient effect.  It may actually be the
rapid heating and consequent fast thermal expansion that causes bulbs to
burn out.  Once a bulb is "lit" the thermal changes are not as severe.  A
possible scenario is that the rapid thermal expansion may cause some coils
to shift and short which produces lowered resistance, a flash, and burn out.
Presumably ramping up the power via a dimmer might make bulbs last longer.

Simulating this type of effect is fairly difficult.  One might be able to
observe shifting of the filament when the light is turned on quickly.  OTOH
maybe the manufacturers have written some papers on these effects and their
solutions.

John M. Clement
Houston, TX

> I salute the experimental data adduced by John and Mike.
> I question the use of AC if the impetus is to investigate localized
> overheating in bright spots at the turn on transient though.
>   DC would show variations a little better?  In the experimental
>   subjects,  it is clear that turn on flash is not seen.
_______________________________________________
Phys-L mailing list
Phys-L@electron.physics.buffalo.edu
https://www.physics.buffalo.edu/mailman/listinfo/phys-l