- #1
feynman1
- 435
- 29
When 2 conductors/dielectrics touch, will surface charges move away from their original conductor/dielectric to the other?
How could any charge move in a perfect dielectric? You are implying that something happens differently, the instant when they 'touch', compared with when there's a small gap. The Capacitance that the conductor will 'see', starts with an air spaced capacitor in series with a dielectric space. As the gap decreases, the capacitance of the air space increases without limit until all that's there is the dielectric layer. Can any charges flow onto or off the dielectric surface? By definition, I don't think so.anuttarasammyak said:Yes, they meet and cancel charges.
I too disagree that charges in dielectrics can move, as there's no free charge there. But what about conductors?sophiecentaur said:How could any charge move in a perfect dielectric? You are implying that something happens differently, the instant when they 'touch', compared with when there's a small gap. The Capacitance that the conductor will 'see', starts with an air spaced capacitor in series with a dielectric space. As the gap decreases, the capacitance of the air space increases without limit until all that's there is the dielectric layer. Can any charges flow onto or off the dielectric surface? By definition, I don't think so.
I think that the clue to the perceived paradox here is that the conductor is a real one and 'all the charges do not occupy an infinitely small region on the surface (the row of +++ signs that we draw in diagrams). The molecular fields in a real dielectric will not be uniform at the surface either.
Different conductors.hutchphd said:Are the metals (conductors) the same or different? The electrochemical potential seems to unnecessarily complicate the discussion, but certainly is necessary for different metals.
I'm not sure why you mean by "cancelled". For two ideal dielectrics the electrons from one side will not flow onto the other side. But, as I wrote before, it is not fruitful to try to reconcile ideal situations with reality. It's called a discontinuity, I think.anuttarasammyak said:surface charges of dielectric are cancelled,
Please find an attached figure to show "cancel" I mean in post #14. Dielectric is also insulator, touching condenser plates.sophiecentaur said:I'm not sure why you mean by "cancelled".
That's fine as an intuitive picture of it but how is that 'cancellation' any different from the same +- patterns that you have drawn all over the dielectric? Wouldn't you expect the gradient of the potential 'within' each molecule to be the same as the gradient of the potential between them? If it were not, there would be movement of charge to make it so.anuttarasammyak said:Please find attached figures to show "cancel" I mean in post #14.
Conductors are materials that allow electric charges to flow freely through them, while dielectrics are materials that do not allow charges to flow easily.
When conductors and dielectrics touch, the electric charges from the conductor will redistribute themselves on the surface of the dielectric. This is known as induced polarization.
When two conductors touch, the electric charges on their surfaces will redistribute themselves until they reach equilibrium. This means that the charges will spread out evenly on the surface of the conductors.
When a conductor touches a dielectric, the electric charges on the surface of the conductor will induce opposite charges on the surface of the dielectric. This creates an electric field between the two materials.
No, surface charges do not disappear when conductors and dielectrics touch. They are redistributed and induce opposite charges on the other material, creating an electric field between them.