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?
When an ideal capacitor is charged by dc battery, charge flows momentarily till the capacitor gets fully charged. Ideal capacitor means infinite resistance for dc.
When an ac source is connected to the capacitor, conduction current, 
continuously flows in the connecting wire. Due to changing current, charge deposited on the plates of the capacitor changes with time. This causes change in electric field between the plates of the capacitor which causes the electric flux to change and gives rise to a displacement current in the region between the plates of the capacitor.
Displacement current is given by, 
