
38-1
Electric-eld strength is dened as the ratio of the force on a positive test charge at rest to the magni-
tude
of th
e
te
st
ch
arge
in th
e
li
mit
as th
e
ma
gnitude
of th
e
te
st
ch
arge
ap
proaches
ze
ro
. e un
its
of
el
ectric-eld
st
rength
ar
e
vo
lts
pe
r
me
ter
(V m
−1
). Electric charges and currents are sources of electric
an
d
ma
gnetic
e
lds,
an
d
Ma
xwell’s
eq
uations
[1
]
pr
ovide
th
e
ma
thematical
re
lationships
be
tween
el
ec-
tromagnetic
(
EM)
elds
a
nd
s
ources
.
e el
ectric
e
ld
at a po
int
in sp
ace
is a ve
ctor
de
ned
by co
mponents
al
ong
th
ree
or
thogonal
ax
es
.
Fo
r
e
xample,
i
n
a r
ectangular
c
oordinate
s
ystem,
t
he
e
lectric
eld
can be written as
E xE yE ...