Engineering Principles V11

Clive W. Humphris

RCL SERIES: RC Series Circuit.  

When a capacitor and resistor are connected in series a current will flow to charge the capacitor. Current I is shown as being in phase with VR. VC will lag I by 90°. The two voltages VR and VC cannot be added directly and the phasor diagram is used to find the resultant or applied voltage amplitude and phase angle.

Voltage VC can be found using AC Ohm's Law where VC = Xc × I.

The resultant or applied voltage is that which is required or developed across the circuit with these particular component values. Note the resultant voltage can be greater than the individual values of VR or VC.

As this is a capacitive circuit the resultant voltage phase angle will lag the current I.

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