When capacitor is connected to a battery, the current is maximum initially & when capacitor is charged fully, the current is zero. How the current flows through capacitor, as inside the capacitor is dielectric i.e.insulator?

Asked by DEEPAK KOTHARI | 17th Oct, 2010, 01:46: PM

Expert Answer:

Dear student
As soon as a capacitor is connected to the battery, charges begin to get stored on one plate, say + charge on plate 1, & which by virtue of polarisation through the dielectric, induces opposite charge, here - charge on plate 2. This results in pushing of + charge through the wire connected to plate 2 towards the battery...the circuit is complete & current flows while the C is charging.
The dielectric (blue coloured slab) develops - sign on side facing plate 1 & + charge on the side facing plate 2. The charge + on plate 1 & - charge on dielectric slab are bound charges as they are held to ecah other by force of attraction.
Similarly - charge on plate 2 and + charge on dielectric slab are bound charges. This results in movement or repulsion of + charge away from plate 2 towards the - terminal of the battery. This continuous flow of + charge along the wires is current flow. But this process of charge separation, charge building on the dielelectric is limited by the extent to which the capacitor can hold definetive amount of charge & definite amount of charge that the dielectric slab can allow building up before the breakdown. That is when we say cpacaitor is fully charges, & thereafter there is no further buidling up of the cahrges on the plates & capacitor wud have reached its max. capacity of charge. We say capacitor is fully charged.
Thereafter the further flow of charges through the wires is stopped & current flow stops.
We hope that clraifies your doubt.

Answered by  | 19th Oct, 2010, 09:36: AM

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