Q1:

Series RLC impedance or voltage totals must always be calculated by

ANS:A - adding values vectorially

The amplitude of the source voltage across all three components in a series RLC circuit is made up of the three individual component voltages, VR, VL and VC with the current common to all three components. The vector diagrams will, therefore, have the current vector as their reference with the three voltage vectors being plotted with respect to this reference as shown below individual Voltage Vectors.

This means then that we can not simply add together VR, VL and VC to find the supply voltage, VS across all three components as all three voltage vectors point in different directions with regards to the current vector. Therefore we will have to find the supply voltage, VS as the Phasor Sum of the three component voltages combined together vectorially.