1. Edward C. Jordan Memorial Offering of the First Course under the Indo-US Inter-University Collaborative Initiative in Higher Education and Research: Electromagnetics for Electrical and Computer Engineering by
Nannapaneni Narayana Rao
Edward C. Jordan Professor of Electrical and Computer Engineering
University of Illinois at Urbana-Champaign
Urbana, Illinois, USA
Amrita Viswa Vidya Peetham, Coimbatore
July 10 – August 11, 2006

2. 4.2 Dielectrics

3. Dielectrics are based upon the property of polarization, which is the
phenomenon of the creation of electric dipoles within the
material.
Electronic polarization: (bound electrons are displaced to
form a dipole)
Dipole moment
p = Qd

4. Orientational polarization: (Already existing dipoles are acted
upon by a torque)
Direction into the paper.
Ionic polarization: (separation of positive and negative ions
in molecules)

5. The phenomenon of polarization results in a polarization
charge in the material which produces a secondary E.

6. Polarization Current

7. To take into account the effect of polarization, we define the
displacement flux density vector, D, as
vary with the material, implicitly taking into account
the effect of polarization.

8. As an example, consider
Then, inside the material,

9. D4.3
For 0 < z < d,
(a)

10. (b)
(c)

11. Isotropic Dielectrics:
D is parallel to E for all E.
Anisotropic Dielectrics:
D is not parallel to E in general. Only for certain directions
(or polarizations) of E is D parallel to E. These are known
as characteristic polarizations.

13. D4.4
(a)

14. (b)

15. (c)