A solid metal sphere, of radius 
, is insulated from its surroundings. The sphere has charge 
. This charge is on the surface of the sphere but it may be considered to be a point charge at its centre, as illustrated in the figure below.
Show that the capacitance 
of the sphere is given by the expression
The sphere has radius 
. Determine the capacitance of the sphere.
A spark suddenly connects the metal sphere in (b) to the Earth, causing the potential of the sphere to be reduced from 
to 
. Calculate the energy dissipated in the spark.
.
.
