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Magnetic Induction
Magnetic Induction
 magnetic flux
 induced emf
 Faraday’s Law and Lenz’s Law
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View Full Document Magnetic Flux
Magnetic Flux
Flux through a surface S:
B
∫
⋅
=
Φ
S
dA
B

a scalar ;
units,
1 T·m
2
= 1 Weber (Wb)

represents “number of magnetic field lines through a surface S”
(
dA
is the “area vector”, perpendicular to the surface.)
Magnetic Flux
Magnetic Flux
Flux through a
closed
surface S:
0
dA
B
∫
=
⋅
S
This is like Gauss’ law, but for magnetism.
However, it states that:

the number of magnetic field lines that enter a
volume enclosed by a
surface S
must
equal the number that leave the volume

and it implies that magnetic monopoles do not exist
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View Full Document Faraday’s Law:
Faraday’s Law:
When the
external magnetic flux
Φ
B
through a closed conducting loop
with one turn
changes
, the emf induced in the closed loop is:
dt
d
B
Φ

=
ε
(for a loop with
N turns:
)
dt
d
N
B
Φ

=
Note that
Φ
B
changes if:
1)
B
2) the area
of the circuit changes (
dA
)
3) the orientation
B•dA
)
( 29
θ
cos
BA
dt
d

=
Lenz’s Law (the negative sign)
Lenz’s Law (the negative sign)
(for the direction
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This note was uploaded on 05/02/2010 for the course PHYSICS 1E03 taught by Professor Jopko during the Spring '08 term at McMaster University.
 Spring '08
 jopko
 Physics

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