Just a curiosity about lamp filaments:
Airplane crash investigation take a special attention to panel lamp
filaments.  They can almost identify if a lamp was on or off at the
crash moment.  Alarm and "red lamps" are important to understand why an
airplane crashed.  A lited lamp has a hot filament that breaks it easily
at a crash impact. A cold filament is more difficult to break... well...
it helps.

ACTUALLY, the analysis of light bulb filaments is a little more scientific... basically the heat from the lit bulb will allow the metal to move in the direction of the crash, so a lit bulb will break, but the broken filament will display a "conical" shape since the near molten metal has moved to one end of the filament.
This is how they can differentiate between a bulb that broke due to being stepped on, and a bulb that was lit.

This technique can be used to tell if a smashed car light was actually on before the car crash totalled the lights. (Used to determine if the drunk was driving with his lights on or off..etc)

Des Bromilow