Chapter 8 Electrical Engineering 153
Semiconductors
Semiconductors are materials with conductive
capabilities between that of conductors and insula-
tors. Silicon is the most common semiconductor.
Semiconductors are used in items such as transistors,
diodes, solar panels, and integrated circuits (ICs).
Sensors
Electronic sensors create an electrical signal
based on environmental conditions. The signal
changes as the environmental conditions change.
For example, electronic thermostats are used in
many homes to tell the heating system when the
house has cooled down and it is time to make
more heat. Inside the thermostat is an electronic
sensor. This sensor can tell what the temperature
is in the home and sends that information through
an electrical signal to the heating unit.
Output Components
Output components are the parts that use
electricity to perform a desired task. For example,
a lamp uses electricity to create light and a motor
uses electricity to create rotary motion.
Incandescent Lamps
As electrons fl ow through a conductor, they
create friction and, therefore, heat. Some conduc-
tors can get very hot. This heat can be used to
generate light. An incandescent lamp creates
light when the current fl ow causes the tungsten
fi lament to get so hot that it glows. The tung-
sten fi lament is suspended inside a glass globe.
All of the air inside the globe is evaluated and
is sometimes replaced with an inert gas, such
as argon. If there were oxygen inside the globe,
the fi lament would burn up due to the heat. See
Figure 8-24. Federal energy effi ciency legislation
has mandated traditional incandescent bulbs be
phased out in favor of more effi cient devices,
such as high-effi ciency incandescent, CFLs, and
LEDs, which are described below.
Gas Discharge Lamps
In gas discharge lamps, the glass inside the
globe is ionized. Electrons are released from their
bonds and are free to fl ow. This causes the gas to
glow and create light. Neon lamps are an example
of gas discharge lamps, but other gases are also
used. A resistor must be placed in series with the
light to limit current fl ow because the resistance of
the ionized glass is so low. Gas discharge lamps
can create the same amount of light as incandes-
cent lamps, using a fraction of the electricity.
Fluorescent Lamps
Fluorescent lamps consist of a long glass tube
coated on the inside with phosphorous and fi lled
with an inert gas. There is also a small amount of
mercury. At each end of the tube, there is a fi la-
ment, which creates a small amount of heat to
vaporize the mercury. Passing electrical current
through the vaporized mercury produces ultra-
violet light, which is invisible to humans. The
ultraviolet light causes the phosphorous to glow,
creating the light we see. It is important to note
that fl uorescent lamps use much less electricity
than incandescent lamps because incandescent
lamps waste so much energy in the form of heat.
Compact Fluorescent Lamps
Compact fl uorescent lamps (CFLs) work
on the same principle as the fl uorescent lamps
discussed previously, but are designed to fi t
into normal light sockets. CFLs have been
around for quite a while, but recent technologi-
cal advancements and concerns about global
climate change have made them more popular.
This incandescent lamp uses a tungsten filament to
create heat, which generates light.
Figure 8-24.
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