Physics 212
Lenz's Law
Lenz’s Law
Examples Using Lenz’s Law
1
Physics 212
Lenz's Law
Lenz’s Law
The induced EMF and induced current are in such a direction
as to oppose the change that produces them.
1.If the external magnetic flux increases, the magnetic field
generated by the induced current is opposite in direction.
2.If an external magnetic flux decreases, the magnetic field
generated by the induced current is in the same direction
direction.
3.If there is no change in the external magnetic flux, there is no
induced current.
2
1
Physics 212
Lenz's Law
Here is an example of the application of Lenz’s Law with an
increasing external magnetic field
The induced EMF and induced current are in such a direction
as to oppose the change that produces them.
r
Bexternal
r
Binduced
I
3
Physics 212
Lenz's Law
Here is an example of the application of Lenz’s Law with a
decreasing external magnetic field
The induced EMF and induced current are in such a direction
as to oppose the change that produces them.
I
r
Binduced
r
Bexternal
4
2
Physics 212
Lenz's Law
Motional EMF
The increase in area increase the flux, the induced magnetic
field acts to oppose this increase.
I
r
Finduced
r
Fexternal
r
Bexternal
5
r
Binduced
Physics 212
Lenz's Law
Lenz’s Law
Examples Using Lenz’s Law
6
3