13), to the circuit shown in Fig 7 1 to get
=
vmsin
t
i R
ω
or   
vmsin
i
t
R
ω
=
Since R is a constant, we can write this equation as
msin
i
i
ωt
=
(7 2)
where the current amplitude im is given by
m
m
v
i
=R
(7