Melting a lightbulb filament

by elegysix
Tags: filament, lightbulb, melting
 P: 344 Does anyone know an approximate voltage needed to melt the filament of a typical 120V/60W incandescent bulb? I'm doing a research project and I've calculated 211V. However, I don't have a power supply capable of delivering it - yet. So for now I can't test my theory. and I haven't had any luck with google. Any help is appreciated.
 P: 627 Incandescent light bulb filaments don't fail by simple "melting". From what I can tell, the tungsten sublimates under too much heat creating spots along the filament that are thinner and therefore hotter. In a regular modern light bulb that sublimation process is offset by the gases in the glass envelope - even if the bulb is not a halogen. I can tell you from many reports that when the neutral in a home circuit is disconnected from ground and the load on each side is unbalanced, light bulbs on the lightly loaded (and therefore higher voltage) side will start to pop. From that, I would guess that a standard 60W bulb will not long survive 211 VAC.
 P: 344 Thanks. I've been modeling their spectra, voltage, current, resistance, and temperature characteristics. I want to cause the filament to fail, and I figured raising the filament temperature to the melting point of tungsten (~3683K) would do it. I calculated that I would need 141W using the stefan-boltzmann law, which translated into 211V after modeling the power as a function of voltage. As you pointed out, I realize there are many more factors involved which I have not yet taken into account. But it's a starting point.
PF Gold
P: 2,726
Melting a lightbulb filament

 I would guess that a standard 60W bulb will not long survive 211 VAC.
not an accurate comment, considering I have lots of 40 and 60 and 75W globes in my house operating at 240V

what is missing is that globes are designed for a specific wattage at a specific voltage

cheers
Dave
 Sci Advisor Thanks PF Gold P: 12,256 I believe that photoflood lamps used to be more or less normal bulbs but operated at about 50% over their normal voltage. They would not last more than a few hours at full volts but produce about twice as much light (nice and blue, too) I just found this link which may be of interest.
P: 344
Thanks sophie, that plot is interesting.

 Quote by davenn not an accurate comment, considering I have lots of 40 and 60 and 75W globes in my house operating at 240V what is missing is that globes are designed for a specific wattage at a specific voltage
I did specify 120V/60W. I think his reply was in context.

Moving on, there was a microwave taken apart in our electronics lab this evening. I suspect that tomorrow I'll have the power supply I need to do this test. I'll update with my results if so.