The variation with potential difference 
of the charge 
on one of the plates of a capacitor is shown in the graph below.
The capacitor is connected to an 
power supply and two resistors 
and 
as shown in the figure below.
The resistance of is 
and the resistance of is 
. The switch can be in either position X or position Y.
The switch is moved to position Y.
Show that the time constant of the discharge circuit is 
.
The fully charged capacitor in the figure above stores energy 
. Determine the time 
taken for the stored energy to decrease from to 
.
A second identical capacitor is connected in parallel with the first capacitor. State and explain the change, if any, to the time constant of the discharge circuit.
