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Since all three
components are in
series, the same current
flows through them all.
This is shown by the
horizontal phasor.
Since the resistor
current and voltage are
in phase, then resistor
voltage is shown on the
same phasor.
CIVIL is a remembering
aid.
For a capacitor C,
current I leads the
voltage V by 90 degrees.
For an inductor L,
voltage V leads the
current I by 90 degrees.
If the voltage across
the capacitor equals the
voltage across the coil
then, since they are 180
degrees out of phase,
their effects will
cancel out and we will
be left with the effect
of resistance only.
Z = R
The current and voltage
in the circuit will be
in phase.
I = V/R
All this happens when
capacitive reactance
equals inductive
reactance.
Since capacitive
reactance falls as
frequency increases, and
inductive reactance
falls as frequency
decreases, then there
must be a frequency at
which they are equal.
This is called the
resonant frequency.
A series resonant
circuit has a low
impedance.
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