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Physics Lecture Resources
Prof. Mineesh Gulati
Head-Physics Wing
Happy Model Hr. Sec. School, Udhampur, J&K
Website: happyphysics.com
happyphysics.com
Ch 29 Electromagnetic
Induction
© 2005 Pearson Education
29.1 Induction Experiments
© 2005 Pearson Education
© 2005 Pearson Education
© 2005 Pearson Education
© 2005 Pearson Education
29.2 Faraday’s Law
Faraday’s law of induction:
The induced emf in a
closed loop equals the
negative of the time rate
of change of magnetic
flux through the loop
dB
 
dt
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ε   d
dt
B
Direction of induced EMF
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© 2005 Pearson Education
29.3 Lenz’s Law
Lenz’s Law:
The direction of any magnitude
induction effect is such as to oppose
the cause of the effect.
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Example 29.9
Use Lenz’s law to determine the direction of the
induced current.
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29.4 Motional Electromotive Force
motional emf; length and
velocity perpendicular to
uniform
ε  vBL
motional emf: closed
conducting loop
ε
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
 
  (v  B )  dl
29.5 Induced Electric Fields
 
d B
 E  dl   dt
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29.6 Eddy Currents
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© 2005 Pearson Education
29.7 Displacement Current and
Maxwell’s Equations
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displacement current
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d E
iD  
dt
Maxwell’s Equation
  Qencl
 E  dA 
0
 
d E 

 B  dl   0  iC  ε0 dt  encl
 
 B  dA  0
 
d B
 E  dl   dt
29.8 Superconductivity
© 2005 Pearson Education
© 2005 Pearson Education
Faraday’s law states that the induced emf in a closed
loop equals the negative of the time rate of change of
magnetic flux through the loop. This relation is valid
whether the flux change is caused by a changing
magnetic field, motion of the loop, or both. (See
Examples 29.1 through 29.7)
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Lenz’s law states that an induced current or emf always
tends to oppose or cancel out the change that caused it.
Lenz’s law can be derived from Faraday’s law, and is
often easier to use. (See Examples 29.8 and 29.9)
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If a conductor moves in a magnetic field, a motional
emf is induced. (See Examples 29.10 and 29.11)
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When an emf is induced by a changing magnetic flux
through a stationary conductor, there is an induced
electric field of nonelectrostatic origin. This field is
nonconservative and cannot be associated with a
potential. (See Example 29.12)
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When a bulk piece of conducting material. Such as a
metal, is in a changing magnetic field or moves through
a field, currents called eddy currents are induced in the
volume of the material.
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A time-varying electric field generates a
displacement current iD , which acts as a source of
magnetic field in exactly the same way as
conduction current.
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The relationships between electric and magnetic fields
and their sources can be stated compactly in four
equations, called Maxwell’s equations. Together they
form a complete basis for the relation of and fields
to their sources.
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END
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