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The capacitor opposes
the flow of ac current,
as a resistor does in a
dc circuit.
This
opposition is called
capacitive reactance, Xc.
It is measured in ohms.
Ohm's Law can be
applied, as in the top
formula.
The bottom formula shows
how capacitive reactance
is calculated.
f is the frequency of
the applied voltage, and
C is the value of the
capacitor in Farads.
It can be
seen from this formula
that the value of Xc
goes down
as the frequency
increases.
It also goes down if the
value of the capacitor
increases.
This means that as the
value of C or f
increases, the
opposition to the flow
of ac current decreases,
and the lamp will glow
brighter.
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