Why the plates bcomes charged as soon as they are connected?

[marvelous]

Hi...why the plates bcomes charged as soon as they are connecetd ?

 

[Crazymechanic]

Well it happens because nature has been made such that opposite charges tend to attract while the same repel , as in a dc capacitor (which I believe is what you were thinking) one plate is attached to the positive terminal of the dc and the other of the negative , normally when you make a path for electricity to flow current forms and the electricity is flowing from one point to another , from a higher potential to a lower one (potential is voltage)
Now a capacitors plates don't touch physically so there is a gap between them so all the electrons that come from the - side of the dc stick as far as they can get which is on the plate.The positive charge coming from the opposite side into the opposite plate does the same thing as they are opposite and they want to get together.Between them is an insulator of some type which prevents current from flowing so all we are left is an charge on each of the plates and a electric field due to them , that field also happens to store the energy of all the charges that have went into the plates.