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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?
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Solution
Ideal capacitor means infinite resistance for dc. When an ac source is used, the current flows continuously, but we know that the capacitor has dielectric (air) between its plates. So, ideally there is no current, and circuit would be incomplete. In real capacitor is charged due to contribution of varying electric field. The current between the capacitor plates is given by displacement current
`D = in E`
`I_d = in (dphi)/(dt) `
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