Week 1: Chapter #4: Electrostatics in matter: 4.1 Polarization P (4.1.1 Dielectrics, 4.1.2 Induced Dipoles Example 4.1)

Learning Outcomes:

In this chapter, we shall study electric fields in matter. Matter, of course, comes in many varieties—solids, liquids, gases, metals, woods, glasses—and these substances do not all respond in the same way to electrostatic fields. Nevertheless, most everydayobjects belong (atleast,in good approximation) to one of two large classes:conductors and insulators(ordielectrics).We have already talked about conductors; these are substances  that contain an “unlimited” supply of charges that are free to move about through the material. In practice, what this ordinarily means is that many of the electrons (one or two per atom, in a typical metal) are not associated with any particular nucleus, but roam around at will. In dielectrics, by contrast, all charges are attached to specific atoms or molecules—they’re on a tight leash, and all they can do is move a bit within the atom or molecule. Such microscopic displacements are not as dramatic as the wholesale rearrangement of charge in a conductor, but their cumulative effects account for the characteristic behavior of dielectric materials.

There are actually two principal mechanisms by which electric fields can distort the charge distribution of a dielectric atom or molecule:

  • stretching  
  • rotating.

In this week, 

 I’ll discuss first mechanism streching. Effect of streching is to produce induced dipoles inside the dielectric and thus polarization.
 

Lecture Plan:

Lecture 1:

Introduction to Electrostatics in matter, Comparison between the Electrostrostatics in free space and electrostatics in media, what are dielectrics ? In which way they are different from insulators?

Lecture 2:

Effect of external field on dielectrics, Induced electric fields, Study of polarization, atomic polarizability

Lecture 3:

Atomic polarizabilty of  a nucleus (+q) surrounded by negative charge cloud (-q)