🚀 go-pugleaf

>> Can someone versed in physics please explain this phenomenon?
>> Given an incandescent lamp with a dimmer switch. The lamp is on.
>> One can then slowly turn the dimmer knob and reduce the light

>The resistance of the filament is very much dependent on its
>temperature.  When the filament is cool the resistance is low
>so that at a given setting of the dimmer most of the energy is

OK.  Agreed, there seems to be a hysteresis in light output vs dimmer
knob setting.

But can anyone say authoritatively, if you slowly ("adiabatically")
vary either the current or the voltage applied to a light bulb
(letting it come to temperature equilibrium at each setting), will
there be a *true hysteresis*, or a true bistable behavior, in the
light versus current, or the light versus voltage curves?  

Or is the hysteresis only in the dimmer-light bulb combination, and
really more in the dimmer's response to a nonlinear load than to any
hysteresis in the light bulb itself?  

(I don't know the answer, but would hazard a guess that there's no
true hysteresis in the bulb itself.)