Chapter 6 Dielectrics,I
Electric Polarization P
Bound Charges
Gauss’ Law,
Electric Displacemant D
In contrst to conductors,
dielectrics have no free charges that
can move through the material under
the influence of an electric field,
All electrons are bounded,
Positive and negative charges can
move in opposite direction with a small
displacement of atomic dimensions.
A dielectric in which this charge
displacement has taken place is said to be
polarized,and its molecules are said to
possess induced dipole moments.(See
Fig6-1)
These dipoles produce their own field,
which adds to that of the external charge.
The dipole field and the external applied
field can be comparable in magnitude.
The applied electric field also tends to
orient molecular dipole moments,so that
the dipoles are aligned with the external
field.
However,thermal motions of molecules
tend to destroy this alignmant.
An equilibrium polarization is thus
established,in which there is a net
alignment,on the average.
The electric field E and D