# Figure 23-1 Magnetic Induction by 61Q2i5E

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```									Magnetic Induction
If the current in the primary circuit is constant,
then the current in the secondary circuit is zero.
When the magnetic field in the secondary circuit
increases the current flows in one direction, and
when the magnetic field decreases the current
flows in the opposite direction.
The magnitude of the induced current and emf are
proportional to the rate of change of the magnetic
field.
Induced Current Produced by a
Moving Magnet
The Magnetic Flux Through a Loop
Magnetic Flux
Find the flux through each
side of the box.
Which flux(es) change(s) with time?
When will the emf and the
magnetic flux be the greatest?
A Dynamic Microphone
The Pickup on an Electric Guitar
Magnetic Tape Recording
Induction Loop for the Hearing Impaired
Applying Lenz’s Law to a Magnet Moving
Toward and Away From a Current Loop

The polarity of the induced emf in a loop is such that it produces a
current whose magnetic field opposes the change in magnetic flux
through the loop. That is, the induced current is in a direction such
that the induced magnetic field attempts to maintain the original
flux through the loop.
How do the accelerations compare?
Lenz’s Law Applied to a
Decreasing Magnetic Field
Motional emf
Which plate is positively charge if
the field increases?
What are the induced currents if I
increases?
Eddy Currents
Quantitative Information from