On capacitors and currents (1)
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On capacitors and currents (1)

[From: ] [author: ] [Date: 12-03-10] [Hit: ]
you may already know that air itself is a dielectric which means its an insulator, as per your concept...........

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an insulator is also basically a conductor with extremely low conductivity.as we cannot have a perfect conductor, similarly, a perfect insulator is also not possible.so delete the notion from your mind as to the fact that current is simply NOT going to flow in the circuit, because that isn't true.now, for your answer......
you may already know that air itself is a dielectric which means it's an insulator, as per your concept.........we are not supposed to see any lightning during storms, which is clearly not true.
however, in the case of a capacitor, there exists an electric field directed from the positive plate to the negative plate whose net magnitude comes out to be "sigma/e" ; where sigma-the charge per unit area of the plate and e-the electrical permittivity if the medium.it is this electric field that causes the motion of charge carriers i.e. the electrons, whose motion causes the net conduction of current in the circuit.

cheers!hope you found that helpful.

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Initially there are no charges on the plates.

But there is a circuit connecting the two plates by a source of emf , externally .

The connecting wires too have no net charges , but has equal amount of positive and negative charges . Though the actual mechanism is different, you can understand the following which is equivalent to the net behavior.

Because of the emf of the source, positive charges accumulate on one plate while negative charges accumulate in the other plate.

In between the plate there is a dielectric medium .

Imagine that in the dielectric medium the charges are made to change in a way such that
the charges are arranged nearly in the following manner

+│ - + - + - + - + - + │-
+│ - + - + - + - + - + │-
+│ - + - + - + - + - + │-
+│ - + - + - + - + - + │-


The left side is the positively charged plate. Next to it there are negative charges in the dielectric and next to it positive charges and next to it negative charges, thus the dielectric medium thought the net charge is zero they are arranged as said above due to the charge on the plates.
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