Chap 12 Dielectrics and Ferroelectrics

1
Chap 12 Dielectrics and Ferroelectrics
p1.9x10-18 esu-cm
12. 1 Basic concept
O

• Electric Dipole moment

H
H
-q
q
pqd
d

• Polarization P dipole moment per unit volume

Total dipole moment
E
2
lt Macroscopic Electric Field gt
E0

E0 Field Produced by charges external to the
body
the fields of all charges that constitutes the
body

• E macroscopic field ( much smoother than the
  microscopic
• field)

Theorem the macroscopic electric field caused
by a uniform polarization is equal to the
electric field in vacuum of a fictitious surface
charge density
s P
P
s -P
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The electric field between the plates is E1
-4ps -4pP
Total macroscopic field
E1 is called depolarization field since it tends
to oppose the applied field E0