Classical Physics II
PHY132
Lecture 19
M t
l
d S
lf I
d
t
Mutual and Self Inductance
Lecture 19
1
03/15/2010

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Changing the Angle between
Changing the Angle between A,
, B
C
id
i
d
if
fi ld
h i h
Consider a static and uniform
B
-field to the right.
A wire loop (
N
windings, area
A
) rotates around an axis
perpendicular to
B
(perpendicular to the paper) with
(perpendicular to the paper), with
constant angular velocity
ω
:
–
Thus only the
relative orientation
of
B
and
A
varies with time
A
x
θ
B,A
=
ω
t
B
varies with time…
–
The change in flux:
ω
B
d
d
dt
dt
B A
cos(
)
d
t
BA
dt
sin(
)
BA
t
cos
d
BA
dt
AB
i e induced EMF varies with time sinusoidally with amplitude
ω
NBA
B
d
N
dt
E
sin(
)
NBA
t
–
i.e. induced EMF varies with time sinusoidally with amplitude
– Numerical example: an
AC generator
:
f
= 60 Hz =
ω
/2
π
,
N
= 500
,
A
=3.0 m
2
,
B
= 0.10 T
E
= 2
π
f NBA =
120
π
×
500
×
3 0
×
0 10 = 57 kV
Lecture 19
3
f NBA =
3.0
0.10 = 57 kV
,
i.e. good for High Voltage power line distribution
03/15/2010