State two different functions of capacitors in electrical circuits.
Three uncharged capacitors of capacitances 
, 
and 
are connected in series with a battery of electromotive force (e.m.f.) 
and a switch, as shown in the figure below.
When the switch is closed, there is a charge 
on plate P of the capacitor of capacitance . Show that the combined capacitance 
of the three capacitors is given by the expression
A student has available four capacitors, each of capacitance 
. Draw circuit diagrams, one in each case, to show how the student may connect some or all of the capacitors to produce a combined capacitance of:
