Question

When an ideal capacitor is charged by a dc battery, no current flows. However, when an ac source is used, the current flows continuously. How does one explain this, based on the concept of displacement current?

Answer 1

Ideal capacitor has infinite resistance for DC. When AC source is used, the current flows continuously with existence of dielectric between the plates. So, ideally there is no current, and circuit would be incomplete. In real capacitor, charging takes place due to varying electric field. The current between plates is given by displacement current.

$D=ϵE$

$I_D=ϵ\frac{d\varphi }{dt}$