Let there be light!

The light bulb was invented in the early 1800's by Thomas Edison and Sir Joseph Swan (they got it correct right around the same time). The bulb is made up of a handful of parts. We all use them everyday, but I know I have no clue how they really work.


-LIGHT is a form of ENERGY that can be released by an ATOM.
-PHOTONS are the most basic units of LIGHT.
-ATOMS release PHOTONS when their ELECTRONS become excited.
                                            LIGHT BULB STRUCTURE
-2 metal contacts that connect to the end of an electrical circuit
-metal contacts attached to wires attached to thin metal filament
-Filament sits in the middle of the bulb held up by a glass mount.
-All of these are held in a glass bulb filled with an inert gas.

"When the bulb is hooked up to a power supply, an electric current flows from one contact to the other, through the wires and the filament. Electric current in a solid conductor is the mass movement of free electrons (electrons that are not tightly bound to an atom) from a negatively charged area to a positively charged area."


-Electrons zip through filament, bump into atoms, vibrates atoms and heats them up.


"Metal atoms release mostly infrared light photons, which are invisible to the human eye. But if they are heated to a high enough level -- around 4,000 degrees Fahrenheit (2,200 degrees C) in the case of a light bulb -- they will emit a good deal of visible light."

BRIGHT, BRIGHTER, BRIGHTEST!

Light bulbs are ranked by their power -- the amount of light they put out in a certain period of time (measured in watts). Higher-watt bulbs have a bigger filament, so they produce more light.

A three-way bulb has two filaments of different wattage -- typically a 50-watt filament and a 100-watt filament. The filaments are wired to separate circuits, which can be closed initially using a special three-way socket.

The switch in the three-way socket lets you choose from three different light levels. On the lowest level, the switch closes only the circuit for the 50-watt filament. For the medium light level, the switch closes the circuit for the 100-watt filament. For the brightest level, the switch closes the circuits for both filaments, so the bulb operates at 150 watts.

http://home.howstuffworks.com/light-bulb2.htm