
Two-Terminal Components
143
and for the sake of simplicity we can adjust the origin of time so that
i
:
co
ospt vtit Vt
VI
==ω+ϕ−
Now, recalling Werner’s formulae for trigonometry
(
scos
1
() ()
=
)
the equation can be rewritten as
1
cos
1
cos2pt VI VI t
MM VI MM
()
()
=ϕ−ϕ
+ϕ −ϕ
The term
is dened as phase shift while the constant term of the equa-
tion, i.e.,
cosVI
MM
ϕ−ϕ
which does not depend on ω, is exactly the real power. This can be both positive
(in which case we talk about dissipated power) and negative (in which case we
talk about supplied power).
Recalling that (Section 1.2.5 in Chapter 1)