Necessity of charge rearragement in capacitors for equal potential differences

[animalcroc]

Consider a two identical capacitors connected in parallel and connected to a battery. The battery is removed and then a dielectric is inserted between one of the capacitors. Why will charge flow from one capacitor to the one with the dielectric? I know the "potential differences in the capacitors must be equal" but it does not make sense how that is sufficient reason to cause a charge imbalance. It seems unnatural how charge would accumulate when they naturally repel.

Can you explain this?

 

[Hootenanny]

Remember that a dielectric has a surface charge that will produce an electric field opposing the electric field of the capactior. So if you like at the negative plate more negative charges will be attracted to the surface charge on the dielectric increasing the charge on the negative plate.