Conceptual question on field/displacement

  • Thread starter johng23
  • Start date
  • #1
292
1
I have a very basic problem in understanding the relationship between electric field and displacement. If a field is applied to a dielectric, it is clear that this will cause the material to polarize, and one can define the permittivity of the material to quantify the size of this effect. Since we can write [itex]D=\epsilon E[/itex], we can also define the inverse permittivity [itex]E=\kappa D[/itex]. But conceptually, I can't make sense of the displacement as the independent variable. How does a polarization give rise to a macroscopic field in the same direction? If anything, a polarization seems associated with a field in the opposite direction (by imagining the situation in the center of a dipole), although I know that macroscopic E&M says nothing about these microscopic fields.

If I think about the case of stress and strain, I can easily imagine how either one gives rise to the other. Where is my problem?
 

Answers and Replies

  • #2
292
1
Ok, the answer is just to take the superposition of the fields from many dipoles. Everything should cancel except the field parallel to the polarization.
 

Related Threads on Conceptual question on field/displacement

Replies
8
Views
5K
Replies
1
Views
910
Replies
4
Views
1K
  • Last Post
Replies
2
Views
3K
Replies
9
Views
7K
  • Last Post
Replies
4
Views
1K
  • Last Post
Replies
4
Views
2K
Replies
16
Views
2K
Replies
7
Views
3K
  • Last Post
Replies
1
Views
2K
Top