Fig(A)

Fig(B)

Employing the symbol g and b, Y=g-jb = (1/RP – j/XP)
Multiplying Y by V to obtain the current I, I=Vg - jVb = V/RP – jV/XP

• Vg shown on the above vector diagram is the component of current in phase with the voltage and is the current V/RP in the resistive branch of the parallel equivalent of ZS
• Vb is the component of current in quadrature with the voltage and is the component V/XP in the inductive branch of the parallel equivalent of Z
• Conductance 1/RP of the resistive branch of the equivalent parallel circuit is the conductance g of the admittance Y=g - jb=1/ ZS
• Susceptance 1/XP of the inductive branch is the susceptance b of the admittance Y=1/ZS.

Observation:

• The conductance g is the reciprocal of RP but not RS.
• Similarly susceptance is the reciprocal of XP and not XS.