8(b) shows the variation of voltage and current
with time We see that the current reaches its maximum value earlier than
the voltage by one-fourth of a period The instantaneous power supplied to the capacitor is
pc = i v = im cos(wt)vm sin(wt)
    = imvm cos(wt) sin(wt)
    
sin(2
)
2
m
i vm
ωt
=
(7 19)
So, as in the case of an inductor, the average power
sin(2
)
sin(2
)
0
2
2
m
m
m
m
C
i v
i v
P
t
t
ω
ω
=
=
=
since <sin (2wt)> = 0 over a complete cycle