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For a perfect plate capacity the $E$-field would only exist between the two plates. If I now connect an wire to both plates from outside, no $E$-field would "motivate" the charges to equalize.

But real capacities do discharge themselves like this very well.

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Perfect parallel plate capacitors have to be infinite, and thus you can't connect them from the "outside." Every finite parallel plate capacitor will always have a fringe field (edge effect) to ensure that $$\oint \vec{E} \cdot \mathrm{d}\vec{l} = 0$$ as required by Maxwell's laws in absence of changing magnetic field.

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  • $\begingroup$ I do not think this answers gives credit to the point of my question enough. I could all the the time minimize the fringe field to almost zero influence or argue that I cannot connect a wire through infinite plates is merely a geometric problem. The point with my question is the same. If there is no E-Field, in the wire, will the charges move? Could you explain more why you wrote that one equation and what you are trying to say? $\endgroup$
    – Niclas
    Oct 18, 2023 at 20:37
  • $\begingroup$ What I am trying to say with the equation is that maxwell's laws require that there is always some electric field outside, so that the loop integral of electric field is 0. $\endgroup$ Oct 18, 2023 at 21:08
  • $\begingroup$ If there is actually no electric field in the wires, then the charges won't move. The reason we see charges moving in real life is because fringe effects are not negligible. I hope it helps! $\endgroup$ Oct 18, 2023 at 21:11

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