How 3-Way Lightbulbs Work

A 3-way bulb contains two filaments, and these filaments have differing wattages. Depending on the setting, the filaments operate separately or together to create the appropriate amount of light. Learn more about 3-way bulbs in this HowStuffWorks podcast.

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Episode Transcript

Speaker 1 (00:00):
Welcome to brain Stuff from how stuff works dot com
where smart happens. Hi, I'm Marshall Brain. Today's question, how
does a three way light bulb work? The answer is
pretty easy. A three way bulb has two filaments inside
of it. The next time one burns out, carefully open it,
for example, wrap it in a towel and hit it

(00:22):
lately with a hammer, and you'll see the two separate
filaments inside the bulb. For the lowest setting, one filament
comes on, it might be a fifty watt filament. For
the next setting, the second filament comes on, it might
be a hundred watt filament. For the third setting, both
come on for a total of a hundred and fifty watts.
Look at the end of the bulb's base you'll be

(00:43):
able to see how the lamp switch controls the two filaments. Today,
there are now three way fluorescent bulbs. In one design
from ge there are two different tubes. Either one or
both fluorescent tubes can be lit to create the same effect.
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(01:06):
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