25(a)]
By analogy to the resistance in a circuit, we introduce the impedance Z
in an ac circuit:
m
m
v
i
=Z
[7 25(b)]
where 
2
2
(
)
C
L
Z
R
X
X
=
+
−
(7 26)
FIGURE 7 11 (a) Relation between the
phasors VL, VR, VC, and I, (b) Relation
between the  phasors VL, VR, and (VL + VC)
for the circuit in Fig