22) into the above
equation, we have
2
2
2
(
)
(
)
m
m
m
C
m
L
v
i R
i X
i X
=
+
−
     =
+
−


i
R
X
X
m
C
L
2
2
2
(
)
or,  
2
2
(
)
m
m
C
L
v
i
R
X
X
=
+
−
[7 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