Joseph Swan Carbon Filaments!
The first practical incandescent lamp was the carbon filament designed by Joseph Swan in 1879. It is consisted of a thread of carbon mounted in an evacuated tube! To obtain a good light source a lamp filament requires to be operated at the highest temperature possible! Efficacy increases with the filament operating temperature because a larger amount of energy is emitted as visible light! As operating temperature is increased so is the rate of evaporation of the filament and therefore the life of the lamp is produced! A carbon filament vaporizes very quickly when its temperature exceeds 1700 degrees centigrade! Tungsten is the most refractory of all metals that is used for making filament material that is used in high performance lamps!
A 1 degree increase in light output would have the effect of decreasing the lamp life by 6 degrees. Operating the filament in an inert gas suppresses evaporation and gives longer life than can be achieved can be achieved in a vacuum lamp! It also gives introduces the problem of convection currents that conducts heat away from the filament to the bulb wall!
General Lighting Service!
This creates a cooling effect but is overcome by winding the filament into a fine helical coil, doing this allows a much higher temperature to be reached. As the cooling of filament induces thermal losses in the lamps efficacy is raised and if further shortening of the filament coil by cooling it again "Coiled Coil" raises efficacy still further! A standard G.L.S. (general lighting service) lamp has an has an operating temperature between 2500 degrees centigrade and 3000 degrees centigrade will have an expected life of 1000 hours. Filament lamps are best operated in their operating voltage above the voltage a lamp's life is halved! Higher wattage bulbs tend to be more efficient than lower wattage ones and the reason for this is the fact that thicker filaments can be operated at a higher temperature, which is better for radiating visible light that is another reason for having a higher wattage bulbs!
Lower Wattage Light Bulbs!
This leads to you using fewer bulbs, you buy fewer bulbs and the cost of bulbs becomes less important! To optimise cost effectiveness in this case, the filaments are designed to run hotter to improve energy efficiency to produce your electricity costs. Smaller bulbs use less electricity apiece, making the cost of the bulb more important! This is why lower wattage light bulbs are often designed to last 1500 hours to
a few thousand hours instead of 750 to 1000 hours. Designing the bulbs to last longer produces their light output and energy efficiency! To minimize your cost of both electricity and bulbs, you should use as few bulbs as possible! It is also fairly well known that a cold light bulb filament has less resistance than a hot one naturally! It is fairly well known that a cold light bulb filament has less resistance than a hot one, a light bulb draws excessive current until the filament warms up! Since the filament can draw more than ten times as much current as usual than when it is cold. Easy to install, easy to use, instant start low cost price, reflector lamps allows concentrated light beams and there are many different versions!