Non-Polar
or Bipolar Electrolytic Capacitor 4.7uF, 16V
Non-Polar and bipolar are both used to describe electrolytic
capacitors which may have a voltage of either polarity
applied. In this particular case, the only indication that
the capacitor is a bipolar type is the absence of a polarity
marking. Often there will be some other indication such as
an "N.P." mark.
The schematic symbol is usually that of an ordinary
capacitor. These need to be used where you can't guarantee
that the voltage on the capacitor will always be in the correct
direction, often due to there being a significant a.c. signal
voltage which inverts the polarity for some of the time despite
there being a correct average d.c. bias on the cap, or when there
is no signal present. (This is a very common mistake seen
when normal electrolytic capacitors are used as a d.c. blocker in
real hi-fi amps and old TV sets. The capacitor dies, but
only after a year or so, by which time you've manufactured
thousands of units)
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