## mathavraj one year ago how does current through one end of the capacitor comes out of the other end?

1. mathavraj

@UnkleRhaukus

2. UnkleRhaukus

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

3. mathavraj

is this electric field uniform or non uniform?

4. UnkleRhaukus

it should be very uniform between the plates, but not as uniform at the edges

5. mathavraj

when the battery is connected first, the current varies gradually..so what happens to the field now?

6. UnkleRhaukus

The electric field strength is equal to the negative of the gradient of the electrostatic potential difference,

7. mathavraj

actually..in lecture 18..prof lewin says that electric field is changing inside the plates, while explaining the concept of displacement current.

8. UnkleRhaukus

yeah the electric field will be proportional to the displaced charge

9. mathavraj

how does charge get displaced through the dielectric?

10. UnkleRhaukus

The charge is only displaced from/to the plates, charge in the dielectric does not more

11. UnkleRhaukus

one plate accumulates charge the other plate looses charge

12. mathavraj

so..is displacement current something hypothetical?

13. mathavraj

@ganeshie8 @Potatoes.ramu

14. Potatoes.ramu

It has a dielectric !

15. Potatoes.ramu

And plates. Charges accumulate on the plates!

16. mathavraj

hmm..yeah..but what is displacement current?and how is it related with a changing electric field?

17. Potatoes.ramu

Displacement current is related to a time varying electric field!

18. mathavraj

okay..so how does the field change?

19. Potatoes.ramu

$D= \epsilon(E) + P$

20. Potatoes.ramu

Where epsilon is the permittivity of free space E is the electric field intensity And P is the polarization of the medium

21. mathavraj

okay..thanx..one last doubt..so the magnetic field varies as long as the capacitor is charging?

22. Potatoes.ramu

Yeah!

23. Potatoes.ramu

tHE flux also changes!

24. mathavraj

okay...now I have some idea abt this..thanx :)

25. Potatoes.ramu

Welcome!! :)

26. mathavraj

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.

27. Potatoes.ramu

I don't know if the charge accumulates in one plate and gets depleted in the other...

28. mathavraj

yes it does..

29. Potatoes.ramu

Okay then :)

30. Kainui

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.

31. mathavraj

you mean no one had thought about a changing electric field till Maxwell came?!!

32. mathavraj

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?

33. Potatoes.ramu

Because of the capacity of the dielectric to store charge!