08-09-2022, 03:29 PM
(This post was last modified: 08-09-2022, 03:36 PM by Mike Watterson.)
Some lamps or valve filaments it's 10% change is double or half life. Maybe vacuum filaments. Hence the valves in 1.5V battery sets supposed to be at 1.35V on AC mains PSU, and a 7.5V battery series system about 6.5 V to 6.8V
The bulbs for 6V battery torches can be labelled as 6.5V or 6V. Their life is short as they are really 4V lamps. Car lamps rated equivalently (not headlamps) are probably really 14V (or 7V for old mbikes and 1950s VW). Colour temperature is a guide on pilot lamps. A same voltage torch bulb can be very white and long life pilot lamps are decidedly orange.
I don't think even regular filament lamps have been a vacuum for maybe more than 100 years. Only valves have a vacuum, though I'm not sure about some straight wire tungsten (festoon?) lamps. I think the big advances in filaments were tungsten instead of carbon, platinum or nickel, coiled coils, pure nitrogen then halogen and noble gas mixes. Tungsten was harder to make and is very brittle. Oddly at first the 1941 RCA B7G 1.4V valves used nickel filaments. Philips perfected more uniform and thinner tungsten for 25mA type B7G after WWII, and also the Russians very thin filaments for rod tubes. Tungsten filaments (rather than ceramic and separate cathode types) need a spring tension at one end. You can see the spring move on some miniature direct filament valves.
Halogen are also exponential as well as Tungsten, but a different curve. They are after all still tungsten filament.
The bulbs for 6V battery torches can be labelled as 6.5V or 6V. Their life is short as they are really 4V lamps. Car lamps rated equivalently (not headlamps) are probably really 14V (or 7V for old mbikes and 1950s VW). Colour temperature is a guide on pilot lamps. A same voltage torch bulb can be very white and long life pilot lamps are decidedly orange.
I don't think even regular filament lamps have been a vacuum for maybe more than 100 years. Only valves have a vacuum, though I'm not sure about some straight wire tungsten (festoon?) lamps. I think the big advances in filaments were tungsten instead of carbon, platinum or nickel, coiled coils, pure nitrogen then halogen and noble gas mixes. Tungsten was harder to make and is very brittle. Oddly at first the 1941 RCA B7G 1.4V valves used nickel filaments. Philips perfected more uniform and thinner tungsten for 25mA type B7G after WWII, and also the Russians very thin filaments for rod tubes. Tungsten filaments (rather than ceramic and separate cathode types) need a spring tension at one end. You can see the spring move on some miniature direct filament valves.
Halogen are also exponential as well as Tungsten, but a different curve. They are after all still tungsten filament.
