Function
Capacitors store electric charge. They are used
with resistors in timing circuits because it
takes time for a capacitor to fill with charge.
They are used to smooth varying DC supplies
by acting as a reservoir of charge. They are
also used in filter circuits because capacitors
easily pass AC (changing) signals but they block
DC (constant) signals.
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Capacitance
This is a measure of a capacitor's ability to
store charge. A large capacitance means that
more charge can be stored. Capacitance is measured
in farads, symbol F. However 1F is very large,
so prefixes are used to show the smaller values.
Three prefixes (multipliers) are used, µ
(micro), n (nano) and p (pico):
µ means 10-6 (millionth), so 1000000µF
= 1F
n means 10-9 (thousand-millionth), so 1000nF
= 1µF
p means 10-12 (million-millionth), so 1000pF
= 1nF
Capacitor values can be very difficult to find
because there are many types of capacitor with
different labelling systems!
Examples:
Circuit symbol:
by http://www.kpsec.freeuk.com/
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