MM0704, Lesson 1
in the figure, there are only 5 of resistance as compared with 200 of inductive reactance and 200 of capacitive
reactance. To find impedance, use vector notation.
Figure 1-1. Series Resonant Circuit
Since the reactances are equal and opposite, they cancel out and the only opposition in the circuit is the resistance. The
impedance of a series resonant circuit is, therefore, only the resistance in the circuit. To find the current do the
following.
(IT means total current.)
Note that the current of a series resonant circuit is in phase with the applied voltage. The power factor of the circuit is
one.
A more interesting fact about the series resonant circuit is concerning the magnitude of the voltage across the coil and
capacitor. The voltage across the coil (inductance) is
EL = IXL = (2) X (200) = 400 V.
The voltage across the capacitor is
EC = IXC = (2) X (200) = 400 V..
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