Transcript Chapter 30

Chapter 30: Faraday’s Law
Summary
part(I)
Faraday’s law of induction: The emf induced in a
circuit is directly proportional to the time rate of
change of magnetic flux through the circuit.
E = - N dFB/dt
where FB is the flux through one loop, and N is
the number of loops (assumed identical).
Motional emf: |V| = El = B l v
Motion through magnetic field -> potential
difference between ends of the conductor.
Reverse direction: reverse polarity!
The induced emf is: E = -dFB/dt = - B l v
The induced current is: I = |E|/R = B l v/R
Chapter 30: Faraday’s Law
Summary
part(II)
The power delivered by the applied force is equal
to the power dissipated in the resistance
(assuming uniform motion):
P = Fappv = I l B v = B2 l2 v2/R = (I2R)
Lenz’s law: The polarity of the induced emf is
such that it tends to produce a current that will
create a magnetic flux to oppose the change in
magnetic flux through the loop.
Example: The magnet and the loop!