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Inductors are coils of
wire.
They may be wound on
tubular FORMERS or may
be self supporting.
The former may contain a
metallic core up its
centre.
Iron cores are used for
frequencies below about
100 kHz.
Ferrite cores are used
for frequencies up to
say, 10 Mhz.
Above 100Mhz the core is
usually air and the coil
is self supporting.
At low frequencies the
inductor may have
hundreds of turns, above
1 Mhz only a few turns.
Most inductors have a
low DC resistance since
they are wound from
copper wire.
Inductor values of
INDUCTANCE are measured
in HENRIES.
Inductors oppose the
flow of ac current.
This opposition is
called INDUCTIVE
REACTANCE.
Reactance increases with
frequency and as the
value of the inductance
increases.
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