A three-way bulb is actually two light bulbs in
one. For example, a 150-watt, 3-way bulb usually
has both a 50 Watt filament and a 100 Watt
filament. To get the maximum brightness (150W),
both filaments are powered at the same time. If
you look at the base of a 3-way bulb, you'll see 3
contacts instead of 2: 100W input, 50W input, and
the electrical return line (common to both
filaments). That's why if you stick a 3-way bulb
into a normal 1-way light socket, it looks dim:
only one of the 2 filaments is lit. Three-way
bulbs use the same amount of electricity as the
equivalent watt single bulb, so the 150W setting
takes as much electricity as a normal 150W bulb.
The advantage of a 3-way bulb is that you only
need to turn on the amount of light that you need,
so you can save electricity. The disadvantage is
that if you burn out one of the two filaments,
then you only have 1 choice left.
To start with how it works, a three-way light
bulb has not one (like a standard light bulb) but
two filaments inside. As you probably know,
filaments can be made to be more or less bright.
The filaments of the three-way light bulb have a
different brightness; we could say "dim" and
"medium". So there you have two levels of light
output (each filament on its own), and a third one
is added by having both filaments "on" at the same
time, where "dim" plus "medium"
The other part of the
question was about "using more electricity". The
exact way to say this, as you will likely learn in
your class, is to talk about using power, and
electric power is measured in watts and sometimes
just called"wattage". The brighter a light bulb,
the larger the wattage - you can check this with
some spare light bulbs at home, which normally
have the wattage printed on them. So yes, a
brighter light bulb uses more power, or "uses more
electricity" as one may say colloquially. Also,
while you are at it, compare an old-style,
filament-based (or incandescent) lightbulb with
one of the newer,energy-saving lightbulbs that are
essentially compact fluorescent lights. It used to
be that you could just tell how bright a lightbulb
was from the"wattage" number. The new bulbs,
however, use a lot less power for the same light
output, so you will often see an "equivalent to
xxxW incandescent bulb"notice on the packaging.
Compact fluorescent lights now even come as
three-way lightbulbs, to come back to your
question, where they use the same principle I have
described for filament-based bulbs.
Click Here to return to the search form.