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The coil opposes the
flow of ac current, as a
resistor does in a dc
circuit.
This
opposition is called
inductive reactance,
XL.
It is measured in ohms.
Ohm's Law can be
applied, as in the top
formula.
The bottom formula shows
how inductive reactance
is calculated.
f is the frequency of
the applied voltage, and
L is the value of the
coil in Henries.
It can be
seen from this formula
that the value of XL
goes up as the frequency
increases.
It also goes up if the
value of the coil
increases.
This means that as the
value of L or f
increases, the
opposition to the flow
of ac
current increases, and
the lamp will glow less.
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