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Chapter 11 Electrical Engineering 237
Capacitors
Capacitors have the ability to store and
discharge electricity very quickly. They store much
less electricity by volume than a battery, but they
can discharge and recharge much more quickly.
Capacitors can smooth out (fi lter) variations in volt-
age and can block continuous dc fl ow while allow-
ing pulses to pass. Capacitors smooth out variations
in voltage by absorbing the spikes and fi lling in
the valleys. For example, the internal workings of
computers require dc, but wall outlets supply ac.
Inside of computers, ac is rectifi ed, or changed, to
dc. This dc voltage can vary a great deal. Capacitors
are used to smooth out or fi lter the voltage.
There are a wide variety of capacitors, but
ceramic disc and electrolytic are the most common.
Both work the same way, but electrolytic capaci-
tors can hold much more charge. See Figure 11-20.
A capacitor is made up of two conductive
plates separated by a thin layer of insulation called
a dielectric. When a capacitor is connected to a
power source, current will fl ow for a short period
of time until the negative plate has gained enough
electrons to reach saturation. This negative charge
repels electrons from the opposite plate causing it
to take on a positive charge. See Figure 11-21.
Capacitors can maintain a charge long after
the power source is removed. When working with
capacitors, it is important to treat them as if they
are charged and capable of delivering a shock.
Integrated Circuits (ICs)
An integrated circuit (IC) consists of multi-
ple electronic circuits etched into a thin layer of
silicon and enclosed in a protective material like
plastic. A dot or notch on the outside of the chip is
used for orientation. ICs contain resistors, capaci-
tors, diodes, transistors, and the conductors to
connect the circuits. Some ICs are very sensitive
to static electricity, or charge buildup. It is impor-
tant to take antistatic precautions when working
with these ICs. See Figure 11-22.
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Figure 11-20. 
Shown are types of ceramic disc and electrolytic capacitors.
Power Supply
Capacitor
A
SPST Switch
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Figure 11-21. 
When the switch is closed, the ammeter will read some
current flow until the capacitor reaches saturation.
Antistatic wrist strap
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Figure 11-22. 
It is important to take antistatic precautions when working
with ICs because they are very sensitive to charge buildup.
One type of precaution is this antistatic wrist strap.