We can rewrite
it as
(1/
)
m
m
v
i
ωC
=
Comparing it to  im= vm/R for a purely resistive circuit, we find that
(1/wC)  plays the role of resistance It is called capacitive reactance and
is denoted by Xc,
Xc= 1/wC
(7 17)
so that the amplitude of the current is
m
m
C
v
i
=X
(7 18)
FIGURE 7