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When the capacitor is connected across a potential difference, current flow in one wire to one plate, and out though the other wire (from the other plate) but not through the dielectric in the middle, within the dielectric an electric field is set up
is this electric field uniform or non uniform?
it should be very uniform between the plates, but not as uniform at the edges
when the battery is connected first, the current varies gradually..so what happens to the field now?
The electric field strength is equal to the negative of the gradient of the electrostatic potential difference,
actually..in lecture 18..prof lewin says that electric field is changing inside the plates, while explaining the concept of displacement current.
yeah the electric field will be proportional to the displaced charge
how does charge get displaced through the dielectric?
The charge is only displaced from/to the plates, charge in the dielectric does not more
one plate accumulates charge the other plate looses charge
so..is displacement current something hypothetical?
It has a dielectric !
And plates. Charges accumulate on the plates!
hmm..yeah..but what is displacement current?and how is it related with a changing electric field?
Displacement current is related to a time varying electric field!
okay..so how does the field change?
\[D= \epsilon(E) + P\]
Where epsilon is the permittivity of free space E is the electric field intensity And P is the polarization of the medium
okay..thanx..one last doubt..so the magnetic field varies as long as the capacitor is charging?
tHE flux also changes!
okay...now I have some idea abt this..thanx :)
correct me if iam wrong...when the battery is connected,the charge accumulates in one plate and gets depleted in another and as the electric field steadily rises ,so the field and the flux vary in the dielectric as a result the magnetic field and flux also vary in the dielectric and so there is a displacement current only till the capacitor charges.
I don't know if the charge accumulates in one plate and gets depleted in the other...
yes it does..
Okay then :)
Yes, you're right @mathavraj charge accumulates in one and an equal but opposite charge accumulates in the other. So this creates a stronger and stronger electric field, but your battery isn't getting any more powerful the more it transfers current from one end of the capacitor to the other, so the change in the electric field with respect to time becomes less and less. The idea behind a displacement current is it's just a way to look at the whole circuit as though there is an actual current flowing through the whole wire, when in reality the displacement current is sort of an imagined term. But a very important one. Originally it wasn't included until Maxwell discovered it and because of it he was able to describe electromagnetic waves since this is what implied the existence of a changing electric field.
you mean no one had thought about a changing electric field till Maxwell came?!!
I mean sorry..i asked it crudely...an increasing current in the wire means increasing field...but what puzzles me the most is why do we consider the change in field inside the dielectric so special than the changing electric field in the conductor wire?
Because of the capacity of the dielectric to store charge!