Edison's discovery of the proper element for the light bulb took hundreds of tries before he finally got it right. In fact, his basic design is so elegant that not until recently has the design changed for the common household lamp.
Incandescent Light Bulbs
Modern incandescent light bulbs all contain a filament usually constructed of tungsten. When an electrical current passes through this filament, it glows. The resistance of the material is such that the electrons in the material become so excited that the collisions of the molecular electrons cause them to emit light and heat. This is why most light sockets are constructed of metal or a high temperature plastic that can withstand high temperatures.
The New Light Bulb CFL
Compact fluorescent bulbs or CFLs are the latest to hit the market as an energy saving device that has made a huge impact on the consumer market. These miniature fluorescent bulbs contain no filament. When electrical power is turned on, the gas inside the sealed spiral tube is ignited. The gas becomes excited from the electrical energy and light is emitted. Very little heat, in comparison to the incandescent bulb, is released. This is one of the reasons for the high efficiency rating of these new type of bulbs. Although all fluorescent mercury, a cancer causing agent, the construction is very rigid and as long as proper disposal is followed, the CFL is very safe for the consumer.
The Conduction of Electrical Power to the Lamp
All lamps have two primary wires that conduct the electricity to the lamp. Whether it is the incandescent or CFL type, the male plug has two main connections: the hot or 120 volt side and the neutral or ground side. The hot side of the rectangular prong is the actual current carrying conductor and the one that can give you a shock. This is the potential side of electricity. The neutral or ground side of the plug is the return path for the electrical power. Since all electricity must have a pathway to flow. The neutral is also tied to the earth ground for safety.
The Wire and Its Many Strands
If you have ever looked at a lamp cord or wire, you will note that the copper conductor is made up of many small strands of wire. Electricity actually travels on the surface of the conductor and not inside the wire itself. Think of it like water in a plumbing pipe. Water travels on the inside of the sealed pipe for water flow. Electricity travels on the outside surface of the water pipe and leaves the inside alone. Stranded wire have a large surface area when you consider the fact that all those small strands have a lot of outside surface area to conduct the electricity. In other words, a whole bunch of little pipes that the electricity can travel on the outside of and flow from the potential side, 120 volts through the light bulb and back to the neutral or ground side.
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