Ph272- General Physics II (Electricity and
Magnetsism)
Lecture 17: Ch. 30 - Magnetic Induction
Key Topics
Overview
- Induced Current and induced emf: If you move a wire
loop in an B-field, there will be a v x B force acting
on the charges in the wire. If the total net force is non-zero,
then there is a current flowing in the wire loop. We call it
the induced current. Since there is a current, there must be
an emf, we call it the induced emf. This process of inducing
emf is called motional emf (because it is created by
moving charges in a B-field).
- Faraday Induction: An emf can also be induced by having
a time-depedence B-field (changing B-field)
- Faraday's Law: Both motional emf and Faraday induction
can be described by one law (Faraday's Law) Emf = - d (Magnetic
flux)/dt
- Lenz's Law: Helps us figure out the direction of the
induced current.
Faraday's Law
- Define magnetic flux: Eq. (26-4) (Same as electric
flux)
- Faraday's Law: The induced EMF is proportional to
the rate of change of magnetic flux, Eq. (26-6).
- Demo of Faraday's Law
- Go throught Examples 26-3, 26-4,26-5 (p.844-5).
Lenz's Law
- Lenz's Law: A rule to tell you which direction is
the induced current, see P. 846.
- Examples: Figure 26-9, 26-10,26-11 (P. 847).
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