
23-1
Electricity can be thought of as a means of delivering power from one place to another to do work.
e la
ws
an
d
re
lationships
fo
r
de
livering
po
wer
we
re
or
iginally
de
veloped
fo
r
di
rect
cu
rrent
(d
c)
.
Po
wer
de
livered,
ex
pressed
in wa
tts,
wa
s
ca
lculated
by mu
ltiplying
th
e
vo
ltage
an
d
cu
rrent
as sh
own
in
Eq
uation
2
3
.1:
P EI
dc
=
(23.1)
e
sit
uation
be
comes
mo
re
co
mplex
wh
en
al
ternating
cu
rrent
(a
c)
is us
ed
to de
liver
po
wer
. Fi
gure23
.1
sh
ows
a sin
e
wa
ve
re
presenting
ei
ther
ac or vo
ltage
. Si
nce
th
e
in
stantaneous
va
lue
of th
e
wa
ve
is co
n-
tinually changing, a numerical quantity is dened to represent an average property of this wave. is
qu
antity,