When a capacitor and resistor are connected in series a current will flow to charge the capacitor. Current I 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. TEST YOUR UNDERSTANDING: The subject is to explore the phase angles across Series Resistor, Capacitor and Inductor combinations. Note the resultant phase angle for the RC & RL series components. For the third topic see the effect of making the voltages across the capacitor and inductor the same. Remember the phase angles for RC & RL series circuits are opposing. Does the voltage applied across the resistor have any effect on the result and its phase angle? You can graphically show the effect by drawing to scale or calculate. Compare resultant angles by placing a protractor against the screen.
