Electromagnetic Induction
Current Induced in a Straight Conductor
Current Induced in a Loop of Wire
Faraday’s Law of Induction
Magnetic Flux
Lenz’s Law
Homework
Current Induced in a Straight Conductor
A conductor of length moves
with velocity through
a uniform magnetic field perpendicular to .
A current is induced in the conductor due to the
magnetic force on charges in the conductor.
Serway/Jewett Figure 23.1
Current Induced in a Loop of Wire
A current is induced in the loop when a magnet is
moved toward the loop.
No current is induced in the loop when the magnet
is stationary.
When the magnet is moved away from the loop. A
current is induced in the opposite direction.
Serway/Jewett Figure 23.2
Faraday’s Law of Induction
The induced emf in a circuit is equal (except for a
negative sign) to the rate at which the magnetic flux
through the circuit changes with time.
The SI unit of magnetic flux is the weber (Wb): 1
Wb = 1 T.m The negative sign is an indication of the direction of
the induced emf.
When applying Faraday’s law to a coil with turns,
an emf appears in every turn and these emfs add.
Magnetic Flux
The magnetic flux
through
ele
a differential
ment of area is given by =
.
Note that the vector
face.
is perpendicular to the sur-
Serway/Jewett Figure 23.4
Example
A 1000-turn coil is 10.0 cm in diameter. What emf is
developed across the coil if the magnetic field through
the coil is reduced from 6.00 T to 0.00 in (a) 1.00 s, (b)
0.100 s, and (c) 0.100 ms?
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Lenz’s Law
The induced current will appear in such a direction
that it opposes the change that produced it.
That is, the induced current is in a direction such
that the induced magnetic field attempts to maintain
the original flux through the loop.
Serway/Jewett Figure 23.16
Homework Set 23 - Due Fri. May 28
Read Sections 23.1 & 23.3
Answer Question 23.1
Do Problems 23.1, 23.3 & 23.6