Properties of dielectrics Apr. 2, 2007

+ Polarization () in dielectric (Sect. 3.6.2):
-- volume density of dipole moment
External induces separation of bound charges
Created and surface charge density and volume charge density ; charge neutrality

+ Relation among , & :
for linear, isotropic & homogeneous
, electric susceptibility and relative permittivity
Example 3.10: Electric field inside a hollow dielectric sphere

+ Properties of dielectrics: linear -- not a function of ; homogeneous -- not a function of space; isotropic -- not a function of direction

+ Boundary conditions (Sect 3.8): Vectors can be resolved into normal and tangential components on a surface, i.e.
In front the surface, medium 1 and behind, medium 2; -- from medium 2 to medium 1
At the surface, ,
Example 3.11: Electric field boundary conditions
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HW #16 Due 4/5/07
1. If , find a) the volume charge density, b) the flux through the closed surface defined by , , , c) the total charge enclosed by the closed surface.
2. Given that in free space for 0 < r < 3cm, for 3 < r < 5cm and for r > 5cm. a) How many regions this problem has? b) Find at r = 2cm. c) Find at r = 4cm. d) Find at r = 6cm. (Note: determine in the corresponding region and notice the the density is uniform so what is the easy way to find charge.)
Extra-credit:
Find the voltage V everywhere in problem 2. (Note: It is better to work the problem from the outer region toward the origin, i.e. find V at r > 5cm first since the reference potential is at infinite distance.)