Since the voltages are out of phase we cannot add the peaks or root mean square (RMS) of
The current through each component is the same.
The peak or RMS voltage through the resistor,
VR is in phase with the current.
The peak or RMS voltage across the inductor,
The peak or RMS voltage across the capacitor,
We can draw the vector sum, of peak or RMS voltages,
VT = ,
as shown in the following graph:
θ is the phase of the peak or RMS voltage with respect to the peak or RMS current.
This angle is calculated as follows:
tan θ = (VL-VC)/VR
As an alternative to the vector approach, this can also be expressed as the complex number
VT = VR+j(VL-VC)
j and not
i is used as the value of
i is used for current.
Fischer-Cripps. A.C., The Electronics Companion. Institute of Physics, 2005.
Copyright © 2014 Barry Watson. All rights reserved.