Question

When an ideal capacitor is charged by 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

When connected to a dc battery, no current flows as capacitor offers infinite resistance to d.c .Whereas since a capacitor offers finite resistance to a.c, current flows through it when connected to an ac source.

On connecting the capacitor to an ac source , the electric field across its plates changes continuously. The displacement current arises due to the change of electric field between the two plates of capacitor.

Displacement current, $i_d=ϵ\frac{d\varphi }{dt}$