4.6 Effect of Alternating Field on the Behavior of a Dielectric Material

Here we will examine the behavior of real and ideal dielectric materials under the influence of an alternating electric field, giving an account of the real situations to which dielectric materials are subjected.

4.6.1 Behavior of an Ideal Dielectric

While most of the above discussion has been for d.c. or static fields, in most practical applications, dielectrics are used under alternating fields. Hence, it is imperative to work out their characteristics in alternating fields.

Let us apply a sinusoidal field

(4.54)

This leads to the development of a charging current, I_c, due to a change in the charge with time which is

(4.55)

(4.56)

The term + π/2 implies that the current leads the voltage by 90° in a perfect dielectric. This current voltage relationship can also be understood from a phasor diagram as shown below.