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Science project idea on how electric lights are produced.
Electric Light Production Science Project Idea 
How electric lights are produced. Observation of an incandescent electric light lamp will show that there is within the bulb a very slender filament, which becomes white hot when the current is turned on. Evidently the condition here is similar to that which we observed in obtaining heat from the electric current. Would you consider the resistance to the current to be greater or less in the lamp than in the wire of a heating device? The wires in an electric stove would melt or become oxidized if raised to such a high temperature. What, therefore, do you consider must have been the great problem in the development of the incandescent lamp? The bulb contains no air. What is the advantage of this?
Very few substances have been found capable of carrying the current and yet able to remain in a solid form at the temperature necessary for the production of light. For many years specially treated carbon filaments were used. More recently, metallic filaments have very largely replaced the carbon ones; the most satisfactory filament being made of tungsten. It uses only about one third as much .electricity as the carbon to produce the same amount of light.
The name which has been the most closely associated With the improvement of the incandescent lamp, as well as with almost every improvement in the application of electricity, is Thomas A. Edison. The voltage of the electricity in the main distributing wires is very high. You will find, however, that the electric light bulbs in your house are probably labeled 110 volts. A current of much higher voltage is dangerous to human life. You have probably noticed on some electric light poles iron boxes from which wires pass to the neighboring houses. These boxes are called transformers, and in them the voltage is changed from 1100 or 2200 volts to 110 volts. Sometimes transformers are used in the house to still further reduce the voltage of a current used for ringing electric bells, running electric toys, etc. To prevent danger from fire, the wires used in a house must be of sufficiently large size to carry the current without being appreciably heated, and they must be enclosed in metal conduits or tubes in walls and partitions. An amount of electricity which might prove harmful is prevented from passing into a wire by means of fuses, which are pieces of metal of a low melting point inserted in the circuit. When the current becomes too strong the fuse melts and automatically breaks the circuit. Wires must all be carefully insulated; that is, covered with a material which will not conduct an electric current. The arc light, which is of very high candle-power, may be understood from a demonstration of the lamps of a projection lantern. It will be noted that there are two carbons, which are first brought into contact to complete the circuit. When they are pulled apart, the circuit is not broken but the current continues to flow across the space, producing the arc. The (+) carbon becomes hollowed out, and the (-) carbon becomes pointed, apparently by the addition of particles of carbon to it. It seems quite clear that particles of carbon jump across the gap between the two carbons.
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