A capacitor consists of two parallel metal plates, separated by air, at a variable distance 
apart, as shown in the figure below. The capacitance 
is inversely proportional to .
The capacitor is charged by a supply so that there is a potential difference (p.d.) 
between the plates.
State expressions, in terms of and , for the charge 
on one of the plates and for the energy 
stored in the capacitor.
The charged capacitor in (a) is now disconnected from the supply. The plates of the capacitor are initially separated by distance 
. They are then moved closer together by a distance 
, as shown in the figure below.
Explain whether reducing the separation of the plates results in an increase or decrease in the energy stored in the capacitor.
