Bulb Life vs battery voltage

[eelnoraa]

I have heard a lot of people says that running a light with lower voltage than its spec will shorten the bulb life. Is this true? Can some one explain to me why please?
From my intuitive, I think runing a light with a lower voltage will make the bulb last longer because it doesn't run as hot. Please explain the reason behind it. Thanks a lot!

 

[Nerd]

For a halogen bulb this is true because if you are not running the bulb hot enough, the halogen cycle cannot be completed effectively. The halogen gas inside the bulb will redeposite the evapourated filament atoms back onto the filament. If it's not hot enough, it will not deposit the atoms back and thus the filament gets thinner faster and is more prone to breakage.

 

[Doug S]

Originally posted by eelnoraa:
I have heard a lot of people says that running a light with lower voltage than its spec will shorten the bulb life. Is this true? Can some one explain to me why please?
From my intuitive, I think runing a light with a lower voltage will make the bulb last longer because it doesn't run as hot. Please explain the reason behind it. Thanks a lot!

<font size="2" face="Verdana, Arial">Your intuition is correct. For incandescent lamps, a 10% reduction in voltage typically extends life approximately by a factor of 4. This relationship is not true for a reduction in voltage in a halogen lamp where the reduction makes the difference between the glass envelope operating above or below approx 200-250C which is the minimum temperature for the halogen cycle to work. Even for halogen lamps, if both voltages result in the glass temperatures either both above or both below this temperature range, the usual relationship of voltage to life is true.