The plates of a parallel-plate capacitor connected to a battery acquire exactly equal (and opposite) charges? Why? Will it be true when the plates are of different sizes?

When the key K of the adjacent circuit is pressed, the needle of the ammeter A is deflected but immediately returns to the original position. Why?

A parallel-plate capacitor is charged by a battery which is then disconnected. Then, the distance between the plates is decreased. What are the changes in charge on the plates?

A parallel-plate capacitor is charged by a battery which is then disconnected. Then, the distance between the plates is decreased. What are the changes in capacitance.

A parallel-plate capacitor is charged by a battery which is then disconnected. Then, the distance between the plates is decreased. What are the changes in PD between plates,

A parallel-plate capacitor is charged by a battery which is then disconnected. Then, the distance between the plates is decreased. What are the changes in electric field between plates?

A parallel-plate capacitor of plate area A and separation d is charged to a potential difference V. The charging-battery is then disconnected and the plates are pulled apart until their separation is $2\mathrm{d}.$ Write expressions in terms of A , d and V for the new potential difference.