Marcel Sarzen, age 12, of Atlanta, Ga., for his question:
HOW DOES A LIGHT BULB WORK?
If it's dull outside, with the sun hiding behind clouds, your teacher turns on the lights in your classroom. She walks over to the wall and pushes a switch. It's that easy now because we have electricity and light bulbs, but it wasn't too many years ago that we were lighting our rooms with oil lamps. The light bulb is something a great many of us take for granted.
Thomas Edison invented the incandescent light. Of the more than 1,000 inventions which he patented and the 3,000 more bearing his name, the electric light was probably his most important contribution to man.
Take a look at a clear bulb. You'll see the base is made of brass, and coming from it is a glass stem in which two wires are sealed. One of the wires is connected to the metal disc at the bottom of the base while the other is connected to the side of the base the part which screws into the socket. The wires coming out of the glass stem are linked together by several turns of wire called a filament.
When electric current flows through the wire filament, heat is generated. The wire gets white hot in the bulb, thus making it give off light.
In early days, light bulbs were made with carbon filaments that were created by charring bamboo splints. Unfortunately, these were very fragile and could not be operated at very high temperatures without vaporizing. These early day carbon filament lamps gave off a yellowish glow and comparatively little light for the amount of electric energy used.
Light bulbs today use tungsten wire for their filaments. Tungsten is a very hard metal, but it is ideal since it can stand very high temperatures without melting or vaporizing.
The lamp's filament is put into a glass bulb to protect the delicate wires from the air. Metal will rust when exposed to air, more rapidly when it is hot. For this reason the bulb around the filament protects it from the air so that it will not burn out at once.
Power of a light bulb is shown in watts, the amount of electric energy being converted into heat in the lamp each second. Where just a little light is needed, a 15 or 25 watt lamp will do the job. Or perhaps you'll need a 40 watt size.
Light bulbs that are too glaring are bad for your eyes, but at the same time you should be sure that your reading lamp is not too dim. Proper lighting is most important for careful eye care.