
39-6 Electromagnetic Variables
Equation 39.10 states that a temporal change in B
⃗
or the mechanical orientation of A
⃗
relative to B
⃗
will produce a terminal voltage. If the coil remains xed with respect to B
⃗
, then static elds cannot be
de
tected,
bu
t
if th
e
lo
op
is ro
tated
or th
e
ma
gnitude
of A
⃗
is ch
anged,
th
en
it is po
ssible
to me
asure
a
st
atic
eld
.
e
r
elationship
d
escribed
b
y
E
quation
3
9
.10 i
s
e
xploited
i
n
m
any
m
agnetic
eld
m
easuring
in
struments
(
see
[
1])
.
Fi
gure
39.4 sh
ows
th
e
tw
o
mo
st
co
mmon
in
duction
co
il
co
ngurations
fo
r
me
asuring
e
ld
st
rength:
the air-core loop antenna and the rod antenna. e operating principle is the same for ...