Brief Review - Phasor Diagrams
The total impedance (resistance) of this circuit is the contribution from both the capacitor and resistor.
The capacitative reactance Xc is shifted by - 90o from the perturbing voltage signal and therefore is expressed in complex form as
Xc = -j Xc
The total circuit impedance is therefore
Z = R - j Xc
In ac analysis both the resistor and capacitor are treated as phasor quantities, so Xc is - 90o out of phase with respect to the
resistor. Since Z is a phasor sum the result is presented on a phasor diagram (or complex plane)
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